If you go to Cathy Howse's website you will see that she never had long hair as a child or adult....read her bio and look at her pics...I think you shouldn't focus on the negative...instead maintain your routine and be patient.
When I was in my early 20's I was broke and had to do my own hair I started to self-relaxer and used heat only once a week when I would wash, roller set and wrap my hair. It grew like never before. I had shoulder length hair as a child but never longer than that. It was close to bra-strap when I started going to the Dominican's for weekly blow outs thinking I needed someone to take care of it now that it was getting long (big mistake by the way!)
In less than a year my hair was brittle and dry I struggled for 2 years after that to get it back into condition...did the big chop went natural and everything.
Now in less than 2 months of finding LHCF and sticking with a good routine and minimizing heat my hair is growing noticeably!
You can do it...don't think negatively. Maybe you won't reach bra-strap but you can make you hair at whatever length shiny healthy and strong!
P.S you say you never had long hair as a child? Well how was you hair taken care of as a child? Were you always relaxed? Did you parent take care of the hair? Most AA's don't know much about taking care of our own hair (Truth in my case) Much less our daughter's. So maybe it's just that your hair has never been properly taken care of. So the only way to find out if you can grow hair long is to start now!