The examples here all make sense and also provide insight to how and why and “why it’s ok” the way @conmama feels!
I will say that I would add that “feeling sad” is natural depending on the WHY of that sadness. More of passing the parenthood torch that you so loved? - that’s ok! Sad because you (anyone, not OP) will not hold the reigns anymore or feeling like you are “losing” your child? - not ok!!! 
I remember my dad playing Fiddler on the Roof, song Sunrise, sunset, over and over.
conmoma - what beautiful advice to give your son - about putting his (new) family first. Family of origin conflicts/prioritization can cause so much trouble. What a gift to take that off his plate.
I would hope to be as generous and open if my S (& D, later!) get married…
Thank you so much! I think of divorce rates. I want my kids marriages to succeed, and anything I can do to help that happen, I will.
It happens. At least you and @conmama will be different to your kids and their spouses. My mom’s MIL hated her; apparently my dad should have married someone from a wealthy family. Seriously.
Things became very unpleasant so my parents went to counseling and my dad was told essentially to choose between his mother and his wife. As a consequence me and my siblings no nobody from our father’s side of the family. First cousins we’ve never met, etc. My mom was determined to be different and after my siblings married told me she had an absolute rule to refrain from any criticism or “suggestions” to them or their spouse. One SIL in fact mentioned this at mom’s funeral.
Early this year, it seemed like one of mine was going to get engaged. I was excited for them, even though they are young, but trying to follow their lead. Then he decided he’s not ready, and didn’t want to talk about it for at least a month. They are a great couple, and I support them however they want to move forward. In this case I feel like “I’m gaining a daughter, not losing a son.” All of our kids are living with their SOs, and we would be happy if they all wound up “as is” for life, but we try hard to live by something like “If you’re happy, we are happy for you.”
Another mom who had her kids late. I’m going to be happy when my son gets engaged! They have been dating almost 4 years and are shopping for what rings they want. They want to go to Europe next summer and get engaged there and then marry 2 years later when S is finished vet school and his gf is finished PA school. I love her and hope nothing goes wrong.
Now my daughter … if she gets engaged to the guy she is living with I will have mixed feelings. He is the father of their baby but I really don’t feel they are actually in love or have a long term future.
Lots of emotions mixed together. When my D got engaged it was not a surprise to any of us so the emotions came at different times along the way…
–First and most important emotion was joy. It is wonderful to see your daughter fall in love with a man who is kind, generous, caring, successful in his job, wanting the same things in life as my D etc.
–Admittedly there were a few times that I felt a bit melancholy like when we took our last long weekend as a nuclear family, when D took his advice over mine etc. But those momentary feelings are far outweighed by my happiness and her finding a great partner and knowing that her life is moving forward in a way she always hoped it would.
Now if only my S would find someone great!
I get that you feel like one stage was ending. That said, honestly we were thrilled. My kid met his wife in 2014 when he was doing a junior year abroad. Since they both went to college in the Boston area it was easy for them to stay together. They were together for 6 years and we were really getting impatient. (Though dh and I put off getting married slightly longer, so of course we didn’t say anything!) We’d met her parents (who are from Hong Kong) when dh was there for a mini-sabattical and like them and they seemed equally happy about the match. The engagement was incredibly short. Basically, once they decided to go through with the marriage they wanted to do it ASAP. I was a little sad that there wasn’t a real wedding, but we hope to have a party for them some day when they are back in the country.
Delighted. Love her and her family.
What I have struggled with is their recent move. They have been 1,000 miles from me but now are even farther. And closer to her parents. In fact, they are with them this weekend. I am feeling sorry for myself about that. Obviously, I am glad that they have family within a few hours drive, but I wish I was that family.
I was thrilled when my first (and only) child became engaged. We love her (now) husband, his parents are great, and it feels good to expand our little family. I did not want her to go through life alone and now it looks like she will not. (Yes, I know that the future is uncertain and things happen, but I have a very good gut feeling about them and I think they are extremely compatible.)
Both of my kids are in long term relationships. One lives with her boyfriend and they intend to get married in 3 years, but I think it will be sooner as they have already looked at venues and rings. The big push is that many of their friends are getting married. My daughter is a little younger than the ‘group’. They tried to buy a house this spring but were priced out of the market.
The other is dating a guy in the army. She wants to be engages, but doesn’t want to get married any time soon. She’s starting grad school in the fall. I don’t think they’ll get engaged or married.
As to how I will feel? For the first it will just be the next step. For the second I’ll be a little upset.
Is she dating my son? 
No, dating Dan, Dan the Army Man. I think it is a good break for them as he wasn’t really sure what he wanted to do (cop, army, law school - pick a job) and seems to have found a good spot in the army. His father was career army but his parents are divorced so I don’t think he was exposed to a lot of the day to day stuff as a school aged child, plus his dad is a surgeon so not always on a base.
I think the big problem is going to be that all his friends have wives and girl friends around and I think he’ll get tired of her visiting once or twice a ‘session’ (he’s in officer’s training so getting sent all around every 3-4 months). If he gets assigned to Hawaii, like he wants, it will be time to make a decision since she can’t just fly there for the weekend.
I was very happy when my D got engaged. They had been together since fall of 2012. They got engaged in 2019 and married last summer.
Ecstatic…and I felt the same way when S2 got engaged. My boys were both 32 when they got engaged after having been with their partners for about two years. I love their wives and couldn’t imagine better matches for either of them. Now, if D could find the male equivalent of her sisters-in-law, it would make me very happy!
Today on the FB page for my daughter’s university, it was the engagement picture of her roommate and the boyfriend she’s had FOREVER (so he was a roommate much of the time too). The school put it on the FB page because they are both grads and he brought her back to propose on campus.
This is one more of D’s friends/teammates/sorority sisters who are engaged. To me, that’s more pressure on my daughter.
@4kids4us this is our mutual friend.
@twoinanddone yes, I saw the announcement on her mother’s FB page the other day and thought of you! I’m pretty sure she is the first of their four kids to get engaged so I’m sure her mom is excited (plus, she is their only daughter of the four).
Now the big question at our house is will D be invited to the wedding. D and her BF have been invited to a few weddings where she wasn’t best friends with the bride and he wasn’t best friends with the groom, but D & BF are a ‘2fer’ as they both played lax so inviting them means the couple doesn’t have to have the ‘plus one’ and waste a spot. This guy was not a lax player but a football player. Darn.
My daughter may not make the cut!
Ha, we won’t make the cut either! We never knew the daughter, only met the parents when our son and their youngest son were in high school and played sports together. But then the mom and I got to know each other much better when we were on the board of the booster club. Then my husband recruited her husband to come work for the company where my husband worked. But, my husband left the company last summer, and our boys have both been out of high school a couple years, so we haven’t seen them in a while! Not that we would have been invited anyway. I only met their daughter a few times when she happened to be home from college. Great family though!