I was benching back in college, and I was repping with 315, and all of a sudden I had a weird pain in my armpit. I rested for a few minutes, then loaded anothe 20 lbs on to do my next set and couldn't press it once without getting help. I knew something was wrong. I didnt do chest for a few weeks after that, and when I did, flat and decline bench made that tendon in my armpit uncomfortable, but incline and shoulder press did not. It took a long time to heal, and every time I start getting heavy on bench for a while, it feels funky and I have to back it down. I believe it came from ego lifting. I hadn't worked out all summer, started juicing, and went from 275 for sets of eight to 315 for ten over a period of a few weeks(muscle memory, had benched like that before)