"The most important thing, especially on a first draft is to remember that it is a FIRST DRAFT. It is supposed to be crap. Give yourself permission to write crap and you’ll be amazed by what happens."--Candace Havens, Genreality
You shouldn't be. If you give yourself permission to write crap, you'll write crap.
I've quoted Ms. Havens out of context--this was part of a much longer post about overcoming writer's block--but I've seen this advice presented many times by many writers, and I find it repulsive.
While a first draft may be imperfect, one should never settle for producing crap. The more loathesome your first draft, the more work you'll have to do to your manuscript to create a publishable draft.
Why create unnecessary work for yourself? Why not produce clean drafts at each stage of the process? Do your best with each draft and you'll find yourself producing fewer drafts. You may even reach a point where your first draft is your final draft.
(And these days, with word processing software and personal computers giving us the ability to revise on the fly, who's to say what constitutes an actual draft?)