For what do you do in the meantime? When you can't concentrate. When there's no point looking to do something you can't commit to if one of the three ever got back to you. Another five levels of Candy Crush? Write a silly poem? Have a wank? And after that?
Actors on the fringe of things must feel like this all the time. No wonder they're all basket cases. That and the fact that they're actors in the first place...
As Woody Allen once said, Hollywood isn't dog eat dog, it's one dog doesn't return other dog's phone calls.