How should I go about quitting weed if I smoked all day everyday since I was 18? I m 21.?

It's marijuana. While it is psychologically addictive it's not physically addictive. If you want to quit then simply stop smoking. You will feel the desire to smoke, but it won't be a craving, and you won't sleep very well for a week (dope produces the chemical that makes you go to sleep so your brain stops producing the same chemical. It will take your brain a few days to start up again). As for the rest of the sh it, well that has nothing to do with your drug taking, don't let it stop you improving your life.

Stay sober minded and drink water more often