I highly suggest a start stop meathod both on your own and with a partner. Work youself until right before orgasm then stop, wait a few seconds then continue to do it untill you cant take it. Do this as much as possible and you will start to last longer. Also, if she wants you to hammer it in, but you cum to fast, just think of something that doesnt turn you on. Think about how the wall is blue, or how the woman on the bike had no front teeth

. Most of sexual excitement is in your head, so use your head to prevent it. You will still enjoy the feeling, but you wont cum if you do it right.