Writing a decent college essay is not an easy task. Sometimes you run with an idea and, in the end, it doesn’t work as expected. You’re going to have to revise. Don’t fret: writing a good essay takes time and, by its very nature, it demands revisions. This is all part of the process. Even Harvard recognizes and stresses the importance of revisions. Revising is as fundamental as writing the introductory paragraph.
Laura Saltz of Harvard’s Writing Center has a handout that you can obtain online: http://www.fas.harvard.edu/~wricntr/documents/Revising.html, and it is indeed a useful tool as you go about revising your college essays.