I'm not a tranny expert, but I'm not so sure you will damage the tranny unless you continually use it by manually shifting. It seems to me like you are using like an autoshift (tiptronic) or whatever it is called. Like the Acura TL or such. I have done it in my '93 Accord occasionally it does not shift abnormally or anything by doing it. I have certainly used it a few times to downshift in a quick stop situation to get the engine power to help in braking.
I also sort of disagree somewhat with the comment on Amrercan car trannies as not being any good. Some of them are bulletproof. A Ford C6 or some of the GM trannies were/are great. The main problem is most people never change the fluid and then wonder why the tranny dies with 80k miles. Even Honda has issues- look at the current tranny failures in the TL's and Accords, etc..