In order to be good at anything, you have to suck first, but it's very tempting to give up and just stop when you realize you suck. You may have heard Ira Glass's advice for beginners, seen in the video above and also retold here at Zen Pencils, but the message is the same: if you think you can't do something, it's not just possible, it's probably likely that you just need to keep working to get through the barrier of suckage before you're any good. Even then, once you're good, you probably still suck a bit, and that's okay.
Some truly awful writing may be all that's blocking you from a wonderful writing career.
I've seen this over and over again with my writing students. This is why I know that when I ask them: "Do you want a writing career?" a "Yes!" answer is all they need.
The desire to write is an indication that you can be successful, if you keep writing.
Being a rotten writer when you start your career is a good thing. You'll get much better. "Not good enough" isn't a stumbling block. It's expected.