Can you email him?

You don't have to send him a novella. Just tell him you know that you were putting up walls today and that you feel awful about it. Puff him up and pay him a compliment (you were trying so hard, you had great ideas, you are so patient, etc.), and say that you will take the session to heart and try to come up with workable goals to discuss with him at your next session. Tell him you are trying and will continue to do so.

I've had disasterous sessions too. I've never gone wrong with a short apologetic email.