I couldn't take the money. I mean ethics and agency rules aside, I just don't think there's any reason to tip me! I've gotten lots of thank you cards and I keep and cherish those. Even from before I started grad school when I was a residential counselor working with kids like 8 years ago! Every now and again I look at all the little cards the kids gave me and I smile.

Write your therapist a note and/or give him a card and express your gratitude. He will most certainly appreciate that. And you will avoid the awkwardness that will ensue when he refuses the money, as he must.