I get that too! I trick myself by telling my self I'll just do a few sets, but once i start then I get motivated and do the whole thing.
Another tick I use is to think of some way I will punish myself if I don't go. I used to force myself to skip a week if I missed 1 day, that worked out good only missed a day once by the end of the week i was chompping at the bit. Could use a dietary restriction also.