I use to be a huge pothead. I would toke 4-6 times a day. From the moment I woak up to when I was hanging out with my friends after school hitting the bong in the circle 4-7 times until I passed out. I will say that it has not really hurt me physically or really mentally for that matter. I really don't understand why it's illegal. Alcohol is worse by comparison, same with smoking.
The first thing I notice is that it destroys your sleeping mechanism. You cannot sleep properly when you go to bed stoned. It takes three times as long to enter REM cycles. You also wake up three times more tired. You do get a very physically relaxing sleep though. This caused me an extreme lack of attendance at school. I think I skipped a hundred and seventy classes in grade ten, a hundred and ninety in grade eleven and about a hundred and ninety in grade twelve. Despite my constant pot smoking I still had spares in grade eleven and in the second semester of grade twelve I had three full spares, leaving me one single class in the afternoon that I often slept through. I think I even skipped an entire two weeks in the beginning of the semester too lol. So long story short, weed doesn't kill you.
But what it does do, is it destroys my pleasure centers and my brain capacity. I am incapable of having proper dreams in this part of my sleep and it totally ruins my "good feeling" in my head. It also cracks me the fuck out and creates secondary thoughts. I draw three times worse when I am stoned because I don't really think or have the time to think before I draw. It's as if I have "fried my brain". In small doses this could be a stimulus instead of "overdosing" and completely ruining my brain mechanisms. One hit is all you need.
Also; since I first got stoned I don't get stoned the same as I use to. Now I barely get stoned, and I do not burn out and my munchies are half there as they use to be. In fact my hunger in general has gone down immensley. I much prefer not to be stoned, to being stoned now.