Commas are your friend, too many periods = painful to read. Learn how to make compound sentences and try your best to not sound repetitive. By this, I do not mean try not to say the same thing over and over again, but rather, try not to make every sentence "sound" the same. To be honest, I got really bored half-way through and thought to myself, I have read thousands of essays like this before.
By the way, I am an English teacher and a freelance writer, and the greatest advice I can give you is: having your essay proofread once is not smart, it is common sense. Having your essay proofread twice is a good idea, but only a bit better than common sense. Having your essay proofread three times is getting closer to being smart... you get the idea.