Why can't my hair grow?

On many groups and fotki albums we hear about women who after one year of being napptural (natural) have had great hair growth, but some of us wait and wait for that to happen to us but it hasn't happened yet. What do we do?
I have been natural for, I really don't know. I never counted, it wasn't really a big decision until after I started trying to style my natural hair. It's probably been about 3 years. I still don't even have shoulder length hair and I'm ok with that now because I realize where my problem lies.

1. I pull on my knots and rip them sometimes and I tug on my hair when I'm nervous (usually during class or a test).
2. I don't eat vegetables that much. I don't even eat the recommended servings for a day in a week.
3. I used to wash my hair with harsh products and/or use many different products week to week.
4. Washed my hair too infrequently.
5. Daily life was very stressful.
6. Don't ever get enough sleep.
7. Ate high in fat foods
8. Didn't moisturize hair as much in the week.
9. Trimmed it a lot in the beginning.

Wow, that's a lot. I take responsibility for my hair not growing enough and so should all of you out there who look up to those women who have beautiful, growing, natural hair because they take responsibility and do something about it.