If we're already out of balance, it's very difficult to enforce that policy unto relationships, or situations. It's very much about self-respect, and deeper still: the kind of love that knows to let up when we're trying too hard; or the kind of self-discipline that gets us to force ourselves to try harder and do our share no matter who's coddling us or letting us get away with things!
Usually people who "try too hard" give FAR too much of themselves: their blood, sweat, toil, life, tears and all that goes with it -- it's too much. Whoever or whatever you're trying to give to is "the cup runneth over" and not in a good way. Giving too much is a waste when it's unnecessary, cannot be handled or appreciated, or abused.
If you've lost yourself, the essence of who you are, feel your spark of life diminished due to a relationship or circumstance; you know you've violated a primary principle of life: to thine own self be true. Sadly, an over effort guarantees a bad result, especially in the long run, because over-exertion leads to burn out. There's no way to achieve martyrdom without being killed.
If you're motivated to always do better and more -- start by doing better and more for yourself. Your job performance and quality of life in every aspect will improve as you make taking care of yourself a real priority. It's not selfish: it's selfless. You'll be more productive and effective in every task. Your work and ability will improve simply by taking time to do things like participating in our weekly service.
That which nurtures your soul and rejuvenates your being isn't "just a game." It's the only game in town; in the universe, and the ONLY game worth playing, and BTW: games are supposed to be fun. As Tian says in her book Quam, "'Let' is a little three letter word that means do not help, and do not hinder." Over-doers, try over-loving instead -- you won't argue with the results, we promise, because you'll be far too happy. :)