oh! don't cancel.
When things like this happen to me (and they do), if I can just go in there anyway, i'm always amazed at what comes out of it in the end.
Yr T is going to be kind and gentle and supportive with you, and show that you have nothing to fear.

i know it sounds very odd, coming from *me*, but hang onto your trust even if with yr fingernails and go... you can do it!