One time in my drawing class, a student said she would work on her drawing until she got tired of it. Then my teacher replied, "So you're going to love your boyfriend until you get tired of him too?"
Just this morning, I saw a professional painter who said he would work on his painting until he got sick of it.
Well, I don't know what to say, but I kinda have to agree with my teacher. Finding a stopping point isn't the same as working on something until you get tired of it...