Anxiety. I used to smoke as a substitute for medication, then the more I smoked the more I realized it was just making me more anxious. Circular thoughts and all of that shit. I stopped for a week a bit ago and decided i'll only smoke on weekends, I smoked for a weekend and just felt miserable, so I decided that I don't need it anymore.
It becomes a habit faster than you realize. It's great if you don't become dependent on it, but when you do, it's expensive and just a hassle. People equate it to drinking, having a drink every day doesn't make you an alcoholic, getting drunk every day does. When you smoke, you get high. Do you get high every day? When was the last time you were just sober? I'll put it like this, if you can go 3 full weeks without smoking weed cold turkey, then you are fine.
If you NEED it to get you through something, then you are dependent on it and you should either slow down/quit. Then again we don't know each other and my opinion means shit comparatively.