Bank balance. House. Car. Significant other. Society has strict ideas of success.
You're an artist, you can't live by that.
Many of those things will still be important to you. But it should be up to you if they are.
Artistic fulfillment is the goal. You want to create the magic your heroes did for you.
My dream isn't a Ferrari. My dream is creating one moment at some point in my career that has the effect on someone that "City Lights" had on me. Or to write and direct something that makes someone feel understood like "Almost Famous" made me feel.
That's why the 'Are you famous/rich/giving up yet?' questions sting so much. Because everyone else is on a different trajectory. I could be famous and rich but I'd be miserable as hell if it all meant nothing. When I watch 'The Social Network', I love it because of how good it is, not because the cast and crew are rich and famous.
The artist doesn't ask 'how long till you get a real job?'. But if success doesn't come the artist starts hearing the voices in their own heads.
That's why you can't have a back-up plan. Being an artist takes everything you got. All of you needs to believe in you. If one part of you doubts your own talent, it probably asks the same things as the office worker: "when will you get a real job?" Don't let yourself suffer that.
Sucess for you should be on your own terms. It should be more about the work than the trappings.