Quick Trigger: Genetic!
Hey, guys, it's not your fault! Premature ejaculation may be genetic, thus the insta-spurt as soon as you get your dick into a woman can't be your fault. Previously, it was seen as psychological, but now it may be heavily ingrained into a man's genes. Now, if only they'll find the source of the "aren't you done yet?!?" that I'm always getting asked.