Had one a little under 2 yrs ago. At the time I was focusing on improving my bench because I sucked at it and it was time to get better. On this particular day I was working the incline and planning on working up to the 250-260 range and practicing with some singles to get the feel of the lift. On my second rep with 225 on the negative it felt as if someone nicked me with a hot razor blade about 4 inches over my left nipple. I was able to finish the rep but knew I was screwed. The tear was in the muscle belly itself so there wasn't much I could do about it. I was able to work around the injury by doing strictly overhead work but I managed to give myself an a/c joint issue about 2 months into it. I've had a couple minor tweaks to the pec since then - once doing weighted pushups and once doing speed/dynamic work. Started to work on my bench again here recently with the help of a slingshot which was a great little investment. I now do all my bench work with the slingshot and all reps are paused. One bad rep can completely change your training.