Have you ever done something that seemed absolutely brilliant

but now seems totally absurd/stupid/naive? In other words, an absolute mistake?

Cramming would be one for me. I think I've gotten to a point where my mind is trained to retain mainly short term memory. When I read it seems like I'm almost always skimming over the pages or something like that.

doing "it" with someone I didn't really love (but really liked) just to get it over with... I also thought it would help me not feel to attached to the 'first'
I think I should've waited and made it a more soulful experience...