When I was in High School my trick was before I went out I would jack off first. Sometimes I would even jack off in her parents bathroom when I picked her up.

Just get older...a lot of things change then
But really, get a patient partner and work on the problem together. The other thing to remember is that most of us here are not the super studs we think we are and we all have had problems like yours at one time or another.

Think of somthing non-sexual. A chair for example.

So seriously, I have the opposite problem. I seem to last so long that I literally exaust myself fucking, but never get to the really good part. It's not a hardness issue, just don't seem to close the deal too often. Not kidding here, it's really annoying, although my girl likes it, but sometimes I just screw her to the point of exaustion too.