Don't stop writing, and never give up. Also, don't be your own worst critic. I can't tell you how many times I have written first chapters, and then re-read them and trashed them because I thought they weren't good enough.
Writing is a process. Keep going, and when you are done, go back and rewrite, edit, make changes, etc. but don't destroy what you've written. Somewhere in those piles of rejected papers, your story lives.