The best answer is probably. Everything in moderation.
Masturbation reduces: energy, desire for and motivation to be with women. Masturbating excessively, and roughly can cause a gradual reduction and eventually complete loss of sensitivity in that part that you love to rub so much.
Understand the power of what you're playing with. Orgasm, which is the usual end result of masturbation, causes a release of endorphins. Endorphins is the good feeling that you get, and basically the same thing people are after that do cocaine. Endorphins are nature's most powerful tool of training the mind and body to perform behaviors.
http://www.medhelp.org/posts/Mens-Health/Too-much-porn-masturbation-cause-ED/show/183203
All these people started out with masturbation and work their way up to more and worse porn to help fuel their addiction, with devastating results to their sex life. It appears to me that whatever your subconscious mind fixes on as the source of the endorphins is what will bring about the erection and eventual orgasm. For these people it was the porn that they masturbated to. For me it was the act of masturbation itself. Presumably for the majority of men, they manage to keep the fixation on the act of them having sex with a woman, at least to the point that they do not have too much difficulty performing.
Presently the medical community says that masturbation is fine. For the majority of people that's probably true. Ask yourself do you want to spend your time pleasuring yourself or earning the opportunity to pleasure and be pleasured by another person.
Not that I'm trying to scare you away, just warn you of the possible issues, and avoid the pitfalls that I and others have fallen into.