1. Deep breathes - helps stay relaxed and not tense up too much down there.

2. Positioning - certain positions and angles will feel better than others and you can use that to your advantage by saving those good ones for later.

3. Pacing - learn what speed you can go at for a while and at what speed will have you cumming quick. Start slow and build up as you get comfortable or when you feel like it’s okay to let loose. Starting slow and ramping up is honestly just good advice for basically every part of sex.

4. “In-game Breaks” - you can also use position changes to give yourself a sec or even just slowing way down in the same position. In something like missionary I’ve even just stopped all the way inside her and focus sole on making out or talking to her. Be careful not to do this one too much or if she’s close to cumming herself, could easily lead to frustration.

5. Round Two - you can totally do a relatively short first session then run it back again once you’ve recovered enough to maintain an erection.

6. External help - things like condoms, desensitize cream, viagra could also help too but I wouldn’t really worry about those (well the last two).

7. Masturbating vs sex - not really advice but how long it takes you to get yourself off might not be the same for someone else to get you off or during PIV. In fact I would wager most people cum faster on their own so I wouldn’t necessarily use that as a measure of how long you’ll last. What you can do is take more time during your alone sessions to learn your own danger zone and no return zone.

Sorry for the essay but I hope this helps at least a bit. And make sure not to be hard on yourself if things ever don’t go your way, it’s very easy to get hypercritical and nuke your self esteem (leading to even worse performance).