Well, the question is, which will be more harmful to you- whatever self-destructive behavior you engaged in, or missing one class?

In the absence of an appointment, what other coping skills can you engage? Do you know any anti-anxiety exercises? Here's a link full of them I like: http://forums.psychcentral.com/post-...ptsd-too~.html

Writing here's a good one, what else has worked for you in the past?

I personally wear a "Keep Calm and Time Travel" button- it reminds me, if I can focus on two days from now, or an hour from now, or whatever period, that things will be different, the pressure I feel to act out will diminish.

Exercise, entertainment, talking to friends, indulging in favorite foods, music, etc. might all help too.