Beware of too tight contact of your string hand with your face. It feels good, like you've got a more solid anchor, but that's about all that's good about it. It can lead to more abrasion of your face, lip, etc., by the string, nock, tab, etc. It can also cause inaccuracies on release, as the relief of the pressure of your hand on your face can deflect the course of the arrow. I think it can also lead to creeping, as you may be more aware of the comforting pressure of your hand on your face and less aware of maintaining back tension that should be holding the bow.
That said, I have seen videos of some really good shooters where the pressure of the string hand against the face, and particularly a finger against the lip, is strong enough to distort their faces until they look like a Halloween mask. So clearly my comment above is not meant to apply to everyone, although it has helped me.