Everybody seems to have really good suggestions to avoid pulling out your hair (like wearing gloves etc...) I thought, hmm, what can I possibly offer as advice, especially since I am still pulling sometimes?
I want to help, too, but I guess the only thing I know a bit about is herbs. And where they're concerned, the best one for stress in my opinion is humble lemon balm! It's a member of the mint family, it grows in lots of people's yards like a weed and seems to be totally overlooked.
I'm just gonna quote from botanical.com which says that Lemon Balm "'comforts the heart and driveth away melancholy and sadness.' "
I started taking it during my rough period of unemployment because it has a reputation for being a safe and gentle herb - and I found that after a week of taking it as a tablet I felt VERY noticeably more cheerful. Chipper even! It was 2007's herb of the year (Google it & see

And it just got really good press from the BBC because in addition to it's cheerful properties it has been helping alzheimer's patients with their memory. (take that, st. john's wart & ginkgo! the backyard weed has you beat!)
Soo maybe this just seems like a big advertisement for Melissa officinalis, but at least it might be growing free in your garden this summer - and I'm not saying it would miraculously make any of us stop pulling our hair out, but it's the best de-stressing, safe, herb I know:) Maybe if you try it let me know if you found you felt more relaxed & pulled less. I want to say I was pulling less while I was on it but because I wasn't consciously connecting stress with pulling my hair out with taking lemon balm I couldn't really say. All I know is that I ran out, haven't been taking it again because I finally got a job offer and I feel a whole lot better about life. However, I suppose I am both excited & a little nervous about starting the new job and have caught myself pulling hair out again - just a little.
(... oh, as a "safety disclaimer" I should maybe mention here I am not and have never been on any prescription drugs and as far as I know lemon balm doesn't interact with anything - but certainly if you are taking other things you'd want to make sure before you started taking it. But, as far as I know it's about as dangerous as Sleepytime Tea. )