From the top of my head.
A girl in the audience flirted with me. Not unpleasant in itself but I started to show off and ran so off I missed the arrangement, got stressed and ruined the entire song to the extent we had to stop and move to the next. Embarrasing, especially since I was trying to look cool.
First song of a gig. I was playing my riff, the song was kind of flat without it so it had to be there, but didn't hear one tone. Had to fix it quick since we had started but had no clue to the reason. Everything should be working. It wasn't the the guitar volume knobs, not the jack, not the amp, not the cord. After an eternity I found out that someone had turned the preamp volume down (a Blackstar HT Dual pedal)) to zero some time after our sound check, when everything was GO. I looked like a confused fool.
On a miniature stage I stood right under a spotlight that was facing the top of my head and was constantly on througout the gig, and hot like a frying pan for crispy bacon. I was sweating like a pig and felt just disgusting, it was running in floods and I had chosen jeans that god sticky. I looked like a sweating pig. A warm summer night, no wind so I was still soaked on the tube going home.
Good thing is it wasn't all during the same gig atleast