One who is contented with what he has done will never become famous for what he will do. He has lain down to die. The grass is already growing over him.

Satisfaction with what you have already done tends to close the door on what comes next. Past work is finished and safe, while the next thing is uncertain and might fail, so resting on the record is always the comfortable option. Taken far enough it stops being rest and becomes retirement from the part of you that makes things. None of which means you should never be pleased with your work.

Enjoy the good thing you did, then ask what it taught you that you have not yet used. Set one task your last success does not guarantee. The aim is to stay in motion, not to be dissatisfied.