I've learned to think in terms of having a long career. Actors can have very long careers that last until the day we die but there will be moments when you'll feel like you're a failure or when you're disappointed in yourself.
The first thing I think about when I wake up most mornings is the fact that I'm tired. I have been tired for decades. I am tired in the morning and I am tired while becalmed in the slough of the afternoon and I am tired in the evening except right when I try to go to sleep.