Sex is
better than you think it will be. Your skills/stamina won't be good the first time (even if they're decent or good they can only get better), but it's going to be awesome--for you at least.
Do some research on technique and tactics. Focus on foreplay; try to get her off first (maybe more than once). Don’t be afraid to burry your head in her pussy try to suck and lick her clit. When you find something she likes, keep doing it exactly like that--don't increase intensity. She won't pay as much attention to how long you last and care even less, if you can get her off beforehand. Go slow, or at least don't be afraid to slow down for a little to help your stamina. You don't have to do puritan missionary sex, though. You can leave it in and grind against her clit, tease her (only go half in, pull it out and massage lips and clit), pull out slow and thrust in hard, do looong slooow thrusts (maybe go hard at the very end). Most men find they have better stamina when the woman is on top. Get creative, experiment and learn.
Enjoy yourself most of all. Let yourself go even if you do blow your load early, let it really go. Don't try to fight it and have a weak orgasm and dribble a little. Large ejaculates are a sign of health and virility (women actually find large cumshots attractive). She will also feel flattered that she turned you on so much. Remember sex is meaningless if the guy doesn't cum. Women are biologically programmed to make the guy cum. When they get turned on and they see you're close they will literally beg for it! Your cum is your gift to them and a reward for a job well done.
If you do cum early compliment her (“you’re so sexy, you fuck so good, I just had to cum”), playfully blame her (“you better not complain, you made me do that”) or get really c/f and say “well, thanks” and act like you’re going to leave in a serious hurry. LOL. No matter what don’t be apologetic, just own it, act like it says something good about her and not bad about you (and it does). Just go right back to foreplay. Women love foreplay and cuddling afterwards. Combine the two and wait to get hard again—you’ll last a lot longer. The average length of intercourse from penetration to ejaculation is 3 minutes!
Women are way more sexual than society wants us to think and they enjoy sex more than men. The clitoris is the only organ on either man or woman that has the sole purpose of pleasure--it has twice as many nerve-endings as the penis, in a much more compact area. Bottom line, sex is like any other part of the pick-up. Be Alpha, take charge, do it for your enjoyment, but also take care of her. Relax, have fun, you’ll be fine.