I've gotten to the point where I almost literally bite my tongue. I'm about to say "I'm tired" or something and I stop myself as the words enter my mouth. I think forcefully, "I'm not going to whine about this, saying 'I'm tired' won't help anything, just keep walking and don't complain," etc. It really is tough. I keep feeling like my feelings need to be heard by others, even if they don't change the situation any.
I'm just hoping that someday I won't have to coach myself through it.