I've thought a lot about stuff like that, too. In many ways, I bent over backwards to please my W in ways that I know a lot of other men would not do for their significant others. I packed our lunches every night, I did the lion's share of the chores, I got her pills and contacts out for her, I bought her lots of gifts, I stayed up late to watch TV shows and movies with her even though I had to go to sleep, etc. So when she left, I thought, "So I guess all those nice things I did for you were for nothing?"
I've read in many places that, paradoxically, the more YOU do for the other person, it seems like the less THEY'LL return. I don't know why that balance occurs, but it does. Once we start investing less in the relationship, chances are they'll start adding more of their share to make up the difference.