It's not enough
It is said that too much of a good thing is not always good. But, that only refers to bad things that feel, look and taste good. When you've been on a job for so long, and the only thing you get from it is a paycheck-it's not enough when you still feel empty. The same goes for relationships. Yes, you come home/go to the same person and everything remains the same, day in and day out. There is no life, spark, or fulfillment that makes you say "I feel so complete" and "I'm more than loved; I'm appreciated". There are other times when people who do have enough don't realize it, and they constantly want more. You have to want and desire more only when its "actually" not enough. But, if you're the type who is never satisfied with anything then you'll never have enough.