Both. Some people are just premature ejaculators by nature. I know i had a bad problem with it until i started taking an SSRI, now I go as long as i want every time. At first, I had no problem lasting as long as I wanted, then out of the blue, I got a new girl when i was like 19 and started finishing in a minute. It lasted until I started taking an SSRI (a type of anti depressant I take for anxiety) which will make you a sex god lol. Your girl will cum 10 times before you finish haha