> inside you no longer really care about what you are doing

IMHO that's okay. Life has given me lots more things to care about, and I can enjoy them more freely because I'm not trying to squeeze a living out of them. Though to be fair I've never worked anywhere that really "sold" me on its mission, and it's actually kind of difficult for me to imagine such a company.

I have a question I always ask when I'm being interviewed: what's your favorite part about working here? The best answer I've gotten is "the work-life balance" and it's been a very good fit for me.