IT is hard, you are right!
Nothing is worth getting worse over. I learned that the hard way too (and it took years of that!) GRRRR Pace yourself. Get the schedule ahead of time on the training. You have the right to ask them to accomodate you, if you ask ahead of time. If you have to be at all the sessions, then ask them to make a 15 min break a 30 minute break so you can go lie down. (I'm amazed at how 20 minutes of dark, cool, quite, calming in a bed rejuvenates me --IF I haven't already overdone
Once you have the schedule, then set yours. The hard part is sticking to it. Have a copy and carry it with you... and when it's time to break, study it and let those around you think AH she has something important to do (it's on a paper!) ROFL.
Don't feel you need to tell them anything. People may push you for a reason, but more often than not it is our OWN expectations that try to generate an "excuse." If you still think you have to say something then use: "I'll catch you later." "I'll be back in a few minutes." "I'm going to go by the room for a minute." "I can't talk right now, how about after...?" The less you tell them, the fewer explanations you have to come up with. Sooner or later you will end up saying, "You know? I have MS." I hope it is on your own terms that you say that, and not out of frustration.
Well, it IS important. Once you realize how much you can enjoy what you DO get done, rather than be miserable the whole time after the first few hours because you're pushing...it will be easier to do what's in your OWN best interest in the future. TC (((Hugs))))