Are there mental or physical benefits to abstaining from masturbation/porn/sex?

All in moderation: This is part of life for almost all men after puberty. If a man tries to go without any ejaculation for more than a few days, he usually has trouble working / studying / sleeping. Tasteful erotica, or thinking of that one special person (present / future) is more uplifting than the dead-end junk that's pornography. Casual sex is dangerous and soon disgusts most men. Choose wisely in all things.

Masturbation: If masturbation is against your religious or spiritual beliefs it could cause you to feel conflicted and possibly guilty.