This quote (“A mind is like a parachute. It doesn't work if it is not open.” if the pic isn't there) seemed to be ever present on Facebook for me for a while. I think someone had put it on a T-shirt and the algorithms had decided that I would want something like that.
I'm not entirely sure, though, that he ever said it. Doing a search on Zappa + Parachute only ever brings up the quote but no actually source -- a song, book or interview -- it just hangs there and we have to assume he said it because a lot of sites have dutifully copied and pasted it from a lot of other sites and every so often it gets propagated by signature. To me it sounds like the sort of faux deep bullshit that Ol' Francesco would have lampooned in one of his songs and, anyway, it turns out that an earlier usage is from the 1936 film Charlie Chan at the Circus. So there's a part of me that likes to think that, if Zappa did ever say it, he was ironically quoting Chan.
My immediate thought when reading it, though, is to come up with counter examples or, well, one counter example.
A mind is like a parachute. If you need to use it you're probably fucked already.