A friend of mine gave notice from her job as an associate professor at a small private university. She taught only the classes she wanted, and only in the way she wanted. The administration supported her with academic freedom. She had a good salary and full benefits, with lots of breaks and every summer off to pursue other projects.

Why leave? "Because it was time," she said. Just because it was a good job didn't mean that she had to do it forever. Everything has a season. 

Some of our mutual friends didn't understand why she was closing the door on an opportunity that had served her well. According to her, though, she had to leave to find something new. The right time to leave is when you're ready, not just when someone else makes the decision for you.