Damn i hear what your saying man, i think me daily smoke keeps me sain, just about. If i go a few days without a smoke i get insomna, nausea, can't eat properly and im generally im just a f8cking asshole to everyone...
problems is smoking kills my motivation and makes me lazy so i end up slacking off college work, which i really hate because i know this is my chance to make somthing of myself.
The key is moderation, when i have work or college ill just have a few bongs in the evening which will help me sleep and eat and i wont have a stone over the next day.On my days off i'll smoke as much as i want and just chill with some mates or whatever. So maybe if you just cut back on your smoking you wont feel so tierd all the time and have problems with motivation, moderation works for me.

peace.