I'm not surprised about the social anxiety part, that can happen to potheads post-pot from my and others' experience. All the same though, the great bulk of my own personal social anxiety post-pot, while I'm in 'withdrawal', if you want to call it that, is about how the pot is still in my system for around 2-3 months. Just something about that really pisses me off...I'm not smoking but it's still in me, in society's view based on testing people for drug history (especially with the hair tests out there), and it's not like I'm high because of that. Just thinking about that fact makes me anxious to deal with society in of itself.
That's getting off topic though...
As far as mental withdrawals, I really don't know, I think you're kind of going a little far there, thinking things are way, way worse than they are. In the last semester I went to college, I went complete cold turkey on smoking pot, which I had done for four years prior, everyday, and I proceeded to have the best semester I had ever had at college, even though I was taking some of the hardest classes I had ever taken in college at the same time, finishing up major prerequisite classes and such. So, I was definitely not mentally withdrawn from my own experience post pot. (EDIT: This semester which I did really well in that I just mentioned, though, came about a month after I had stopped smoking and had just been relaxing at home doing nothing for a few weeks...so I did have a period where I could just recoup and chill. That's actually a pretty important point to note - it does take some time to get in the full swing of things after CHRONIC use, but not all that long, really.)
If you want my opinion, you're just blowing things out of proportion. Stopping chronic use of smoking pot is easier for some than others, but all it is is just you not getting high anymore. Just use mind over matter if you have to. Because it's really your body that's undergoing 'withdrawal', and, at least from a medical point of view, withdrawing from smoking any amount of weed a day is relatively tame, no? At least when compared to tobacco, alcohol, heroin, opiates in general, amphetamines/meth, the list goes on and on. Going cold turkey on weed by itself shouldn't be able to zap your mental strength or ability to think and work...even though you can think that it will. Clearly that's what you think has happened, though, and I don't have a definitive response for that.
Anyway, I'm not expecting you to agree with me, but I have been there myself.