Premature ejaculation at 18 years old. how do i train my penis to be better?

Multiple issues: Assuming there is no medical issue, it is thought that masturbation may lead to some issues, since the goal is usually to ejaculate quickly. That said, a lot depends on what the idea is of "premature", 1, 5, 10 minutes? Before she's done? Sometimes thinking of something else can distract a bit, and extend the time. If this doesn't work, consult with a urologist for an evaluation.

Relax: Your hormonal changes have a lot to do with it. Sure, you can think about baseball, etc., but perhaps you can go for round two. Enjoy living, just make sure you wear a condom!