As for busy days or travelling, I use an app that creates these bodyweight circuits that one can do from anywhere. I accept that since anyone can do them from anywhere there are no excuses not to do them. Building the willpower to do something when you dont want to do something is the primary battle.
I don't care if you're working 40 hours or 120 hours. These workouts can be done on a train, in an office, on the bus, etc. I feel like when you acknowledge that and pump yourself up, you're waiting for that realization to so it. But the truly disciplined person doesn't wait. When they feel miserable and every fiber of their being is telling them they shouldn't work out, then standing up and doing it will build your character.
I reference the story of Prometheus doomed to push the boulder up the hill for all eternity. When you are sore and descending the hill realizing you have to push the boulder up for no reason or meaning whatsoever, that is when you find a semblance of character.
When traveling, I love trying new classes or even adventuring to the hotel gym. I'll wake up earlier and take that adventure.