I was wondering why whenever I masturbate my stamina is low yet whenever with a woman I last longer and the climax is much better. I do not masturbate often only when necessary but I always thought self enjoyment helps sexual stamina and helps pre-ejaculation.

So when you masterbate, you ejaculate more quick?
If that's the question, I wouldn't worry about it. Your doing it for your own satisfaction, your not taking time to please another person, nor are you trying to slow down the climax. Your simply trying to get off. If it bothers you, then slow down a little. Just as your about to ejac, stop completley for a few seconds and then go again.