If you can't imagine someone reading your stuff, write a journal.
College admissions officers are generally nice people, sometimes smart enough to have been admitted to the universities from which they are now rejecting thousands of applicants, who read huge numbers of files from identically-qualified students. Much has to do with personal preference and the reality of the numbers.
Instead, you have only to pose an interesting question and wrestle with it.
Here's what I believe about writing: We write to make people fall in love with us.
There's nothing you can do if the person on whose desk your file lands loves Eagle Scouts and student body presidents and hates poetry and you happen to be an anarchist poet who never goes outdoors.
But that doesn't mean you can't write an essay that will show off who you are and why you would be someone they'd want to meet.
In an essay, what matters is not the subject but what you make of it.
If you did the Boston marathon as a bandit when you were sixteen, bully for you. You ran the anchor leg of the 4 x 400m and you made up a huge time deficit so that your team could win the state championship? I'd be more interested if you dropped the baton and lost, because that would give you something to think hard about.
You're able to boil it down to a simple description (dead grandmother), an equation (running=life) or a word (violin).
When you teach creative writing, as I do, you hear from lots of people who say they love to write. Like Dorothy Parker, I love to have written, but I find the work of putting those words on the page far more exhausting than running the gnarliest 50K.