Premature Ejaculation. It can and does strike at the worst of times. Kind of like cancer, but not nearly as funny.
Premature ejaculation is a surefire way to piss your wife/girlfriend off. Premature ejaculation has plagued humanity ever since God created Eve. 40% of men suffer from premature ejaculation, 75% have experienced it before, and 100% of men that say they never have are fucking liars. There are several cures out there for this annoying problem from pills to hypnosis:
Thinking about baseball is not a cure. This only makes you really, really gay. The only known cure that works 100% of the time is to masturbate furiously for several hours before attempting intercourse.