Is masturbation always a sin?

We are humans and have needs. the longer the sperms stays inside the body the more you want to get it out. that is why the sexual thoughts are more frequent and stronger.

People say to get married and have normal sex with your spouse instead of having sex unmarried or masturbating.

Getting married is not that easy. you do not find a woman and say to her "hey lets get married"

some people want to get married but cant find a woman and stay single for a very long time.

Does this means they must not masturbate? if a 18 year old cant find a woman for the next 10-20 years. does this mean he must never masturbate? is that healthy?