>> How do you explain to someone the tremendous letdown that happens when your therapist has to cancel? You are relieved and yet traumatized at the same time.
you work (consciously and unconsciously) on what transpired in the last session, building toward the next one, you prepare, you even brace yourself, because the work is hard - and then the cancellation, it's all postponed and you have to start over with a lot of it. To me it's very understandable ... to feel the cutting of the continuity, like a cutting of the rope that strings from session to session.

>> We are grown men and women in here.
really? I wonder about that sometimes. Part of the reason we need therapy, in many cases (including my case). just my $0.02 though

>> What is the magical power that our therapists hold? What is it that draws us in and makes us want to stay away at the same time?
excellent questions. To me it's the fact that they can help us see, where before we could not; we so much need to gain that sight, and learn to put it in work for our healing; but therapy is hard, so hard, and so we are hopeful and daunted at same time.

>> I am already counting [...] about 336 hours, and 20,160 minutes. [...] I wonder if therapists know that we think this way.
I have a feeling they do but prefer not to think about it.

hope yr DH is helpful in getting you through the next 336 hrs.