"I hated every minute of my training but I told myself 'don't quit'. Suffer now and be a champion the rest of your life." -Muhammad Ali
I found that quote in a small book of quotes I received from my grandmother (I think). It has a lot of similar quotes but this one is my favorite. Originally I'd recite it to myself during Tae Known Do practice to encourage myself to finish my work out or learn a form etc. Now I recite it during revisions. They are tedious (pay attention to every word and think of ways to make them all better), depressing (all of them can be made better) and time consuming (did I really just spend four hours at this!?) but absolutely critical to the writing process. Now I can read them and smile at the improvement.
Don't be discouraged by bad drafts. The first draft is ALWAYS bad. The second draft is less bad, the third might stop making you feel like a loser, and by the fourth draft you might feel comfortable giving it to a beta reader. Suffer through it and you'll be a champion the rest of your life.