Can my essay about an experience that helped define me be about when I was pretty sick for a long period of time? Not sure if that is cliche or frowned upon or anything. Thanks!
As long as you focus on the positive aspects and how it has impacted you and shaped your worldview, you should be fine.
Sure.
Just be sure not to focus on the illness itself but rather how it impacted your life, helped you to grow as a person, etc.
It takes a good writer to turn a huge negative - a long illness - into an the kind of essay that makes the reader say 'What an interesting person! I’d like to get to know him/her better. I bet he/she will bring a unique perspective to our community." If you are up to the challenge, by all means give it a shot. If not, let your guidance counselor address the illness (as a challenge overcome) and use the ‘real estate’ in the application to talk about your goal, aspirations, and what you have to offer the community that accept you.
^^ Agree.