What is your believe on the notion that more knowledge makes one happier?
Knowledge is crucial. Without knowledge, people are nothing; like a tree without its fruits. There would be no cars, no concrete buildings and no glasses that ease life. Earthlings need knowledge to expand their view on something. Although some claim 'Ignorance is bliss', I believe that knowledge can make one happy because one could enlarge one's imagination with the help of knowledge.
Nikola Tesla is one of the best inventor of all time or he used to be called as 'The Genius who Lit the World'. Radio, X-ray and hydro power are few of Tesla's inventions. Tesla loves seeing his mother inventing small electrical household during her spare time and someday he would build one of his own. He goes to university to learn more about electrical power. With his knowledge, he has come to an idea of an alternate current. He starts to imagine a world with his invention, the alternate current. Then, he goes to the city to find Thomas Edison, the one who created direct current. Everyone has been using direct current at that time and Tesla said to Edison that he could invent something more useful to step up power easily which is the alternate current. Tesla creates an induction motor from all the knowledge that he got and he succeeded. He opens a lighting shop and his alternate current has first been used for hydroelectric power in Niagara Falls. He feels contented with his knowledge that leads him to invent something by himself.
Furthermore, Louis Braille is also an example of a person who values knowledge. Braille is blind since she was three because she plays with his father sharp tools. Being a blind person, Braille misses his study. At that time, there is no machine to help the blind to study. However, as she is a brilliant child, she gets to enroll in a university for a blind youth. With her knowledge she builds a Braille machine to help the blind to read. She feels very happy with her knowledge that has helped to expand her knowledge to build a useful machine for the blinds. For her, knowledge is precious.
Therefore, knowledge is invaluable. Knowledge does make one happy as it could enlarge one's imagination such as it does to Nikola Tesla and Louis Braille.
*its my first time taking SAT, I know this essay is pretty bad. I appreciate all of your comments 
What is this essay for? Is it a practice essay for the SAT?
When you’re talking about things that happened in the past, you should generally use past tense. I could give you specific examples throughout your essay if you don’t understand where this should be used.
More importantly, though you have some good examples of knowledge that has benefited mankind, the essay needs much more of your own individual insight. You should comment more on how exactly this knowledge brought happiness to humanity; you have summarized the lives and careers of Tesla and Braille, but have skimmed over the most important part. Spend less time summarizing facts, and more time synthesizing them with your overall argument.
Remember that you are expected to persuade the reader of your point, not give him a history lesson. Let me know if you have questions.
Ohh thanks @music1990. Yeap this just a practice. Its means that I actually have to tell more about how knowledge makes Tesla and Braille more happier right? I know its a bad essay, thanks for your comment, it makes me clearer now, I kinda get nervous when answering as I have to think of the evidences and write them in 25 minutes. I have a question, do we need to include reason like, why do I say knowledge makes one more happier in my essay? Or I just have to say that I’m agree or don’t with the statement and just proceed with my evidence? And btw, I would need your examples too Thanks for helping!
Yes, you would want to say more about how and why knowledge has made them happier. For example, Braille’s invention has allowed her and other blind people to communicate with the world in a way they never could before. That would probably be a liberating experience for someone who hasn’t been able to read. In this case, knowledge provided a way of connecting people with the outside world, who before may have felt isolated.
You could probably use hypothetical examples that you create yourself as well.
You should also search for SAT writing tips online, as I’m sure there are guides to what exactly they are looking for on these essays. I never took the SAT, so I’m not quite sure how they are graded. Hopefully someone else will reply that knows more about SAT in particular. There is an SAT sub-forum that would be a more helpful place to post this: http://talk.collegeconfidential.com/sat-act-tests-test-preparation/
I would explain more about past tense, but I’m not sure how much grammar matters on these tests, and I don’t want to confuse you more if it’s unnecessary. Generally though, when you’re talking about historical facts, you would say, “Tesla went to university” rather than “Tesla goes to university,” because these things happened in the past, not the present.