You can't really quit masturbation. It's in the nature of all us male's. Also it wouldn't be beneficial as masturbating is healthy (but not too much). If you try to make a research about masturbation, they say once a week is healthy or even up to 3 times.
Some say once a day is fine but others say that is too much. The thing to consider here is that you are fine as long as you don't hurt yourself, you don't waste too time much on masturbation, you don't get addicted like doing it right after you just had one. Whatever your reason is for quitting, it's not a good idea.
But if you want to slow down on masturbation try finding some other hobbies that you can do with your hands that will take both your hands and mind off the masturbation.
Get out there and ride a bicycle around or some other distraction. Slowing down on masturbation is really hard when you're 14. I used to masturbate a lot myself and had a sore penis from it but the soreness went away and I wasn't harmed.