I missed the big downturn twelve years ago because I procrastinated. My 401k money was in some fund that was no longer being offered, so the money was transferred into a currency fund (I don't recall what it was). I kept meaning to move it to an index fund, but never got around to it and then the market dropped. A year later I did the transfer and as a result I did very well.

I haven't touched it since but now with yield curve warnings popping up, I'm starting to think I should.