Dear T,
Sorry to be so annoying and ask for another possible schedule change. If you can't, all good--I just forgot about a professional call I should be on at the time of our session. Please know this isn't any form of testing you or wanting between-session contact (I'm sure MC would think at least the latter...) I seriously was just reminded of the meeting in an e-mail this morning! And seeing you is still more important to me than the meeting, so it's fine if you can't change times.
--LT

PS/ETA: Thanks for getting back to me so fast and being able to make the time change. I was going to add an apology to my response for changing the time so often, but then I realized that would suggest I wanted another response from you/reassurance. So I just left it at "Great, thanks, see you then." See, I'm learning! (Might mention that in session.)