novanative
For those of us who had one bad semester in college or are part of some great volunteer society among other things, there aren't too many different ways to explain it in an optional essay.
Given what happened at UCLA with the Turnitin program though some essays there were obviously totally rigged, should we all be worried about using large portions of the same optional essay in our applications? That now scares the absolute hell out of a lot of people because now we have to reinvent the wheel.
If your question is should you be worried about "plagiarizing yourself" so to speak, using the same optional essay across applications, I think that's fine (make sure you don't reference the wrong school though). What the UCLA kids got in trouble for was plagiarizing other people's essays from the Internet or published resources or for a consultant using the same essay for different applicants (which is a double foul since consultants shoudln't write essays in the first place) That's what the program scans for.
As long as they are your words, I don't see a problem leveraging essays you've done elsewhere, as long as you make sure to answer the question. What I did, in my essay writing was started from scratch in each case but had my other essays opened for reference. That way I ensured I tailored my response to each school.