Certainly for my father, there were great times, good times, not-so-good times. He might be shooting a Fellini film for six months, then not working for two months. I'm used to that dynamic.
And then the last album, 'Get It', was done over a shorter period of time and I started using other musicians, as opposed to playing all the instruments myself like I did on the other two.
Confidence, knowing for certain that the person making the call has your safety foremost in their mind. And knowing that the job you are about to take on is the right thing to do, that it makes sense.