If you have to drive to therapy, please don't drink. You will put others at risk.

This really is a BAD idea. If you aren't up to going to therapy, cancel. But don't self-medicate with alcohol. You mentioned a mixed episode. If you are BP, alcohol is only going to make the episode worse. Why are you in self-destruct mode? Rather than getting drunk, how about writing down some ideas about what you are feeling, or trying not to feel, and taking that with you to your appointment.