As of yet, I don't think there's actually any scientific prove that it's physically bad for you. It can become an addiction, though, which could cause inappropriate amounts of admiration for ones own genitals and lack of attraction to other human beings. Still, the rules of being addicted are rather blurry as it is one of those self-diagnosed afflictions/diseases. You have to reach a fair amount of masterbation sessions a day to be called an addict by others, I reckon. As far as I can see, it hasn't had any adverse effects on my life, though. It can release a lot of stress and there's been scientific research that shows that it can better mental health and decreases the chances of getting prostate cancer. I guess what I'm trying to say, is that it might be a good thing, but just as a lot of things moderation's key
It's neither good or bad.
EDIT: You came out of the shadows and made my previous remark slightly redundant. Bless you ^-^
its good