This summer I spent a week mentoring entrepreneurs at the Unreasonable Institute in Boulder, CO. One of my fellow mentors, Tom Chi (at the time Head of Experience for Google X - essentially the guy who worked on the self-driving car and Google Glasses and god-knows what else they cooked up but haven’t yet released), told the entrepreneurs his acid test for how to know when it’s time to stop and do something different:

When you come home from your job in the evening and pretty much all you want to do is slouch on the sofa, watch a movie and have a beer: Quit your job.

When you come home from your job in the evening and you feel pretty indifferent about what you want to do: Quit your job.

Only when you come home from your job in the evening and you feel more energized than in the evening you know that you have the right job (or are doing the right thing).

Whatever you do - it should add energy to your life, not sift it away.