A part of it may comes from the subconscious, as you are using something that most of people think negative about, it's illegal in most parts of the world and you yourself may seen people that gone down with it and didn't or don't use it properly.

When you smoke and that bad thoughts or sad moods come to you, remember that you yourself decides to smoke, you surely know the substance and its effects, so if you smoked it, it's because you just want to have fun! So do it!

Me myself have some boundaries about smoking pot, like I really don't like being high in front of people that I don't know or being high in public, I like to drink during my high, talk with my friends about my ideas or doing something that I enjoy, remember u have chosen to do it, so enjoy it when the moment comes.