How bad is a B?

So now that school’s over I got my first ever B and it was in Music Theory. I had a 99 in the class up until fourth quarter, where I faced stress and anxiety issues and my grade dropped to a 86 (got a 47 4th quarter). I got straight A’s in all my other classes (Lang, Calc BC, APUSH) and have excellent EC’s. Will this impact my chances of getting into schools like Duke, Columbia, and Princeton?

It won’t hurt you. It won’t look good if you’re planning to major in music, but if your overall UW GPA is 3.8+/4.0, you are still in the game for those schools.

FAQ: http://talk.qa.collegeconfidential.com/what-my-chances/1525399-if-you-are-asking-for-your-chances-to-ivies-and-other-top-schools.html

Mantra for the HS student:
Do not think 'Every point I get off of a homework or test is a point away from going to Harvard."
Think: “I need to do my best, and there will be a college that is right for me when I graduate.”

Do not think “If I don’t go to an Ivy League School/Top20, I am doomed forever.”
Think: “No matter where I go, I can bloom where I am planted. I can get involved and shine.”

Do not think: “My life is over…the kid in my math class is taking 20 APs and I am taking 5. I will never succeed.”
Think: “I need to challenge myself, but only to the point where I can still do well.”

It’s all a continuum. There is a small marginal impact to a B. Quite small. You need to pile up several of them before it makes a meaningful difference. One does not do it.