Economists are growing more and more interested in the emotions. My colleague Dan Houser, for example, tells me that interesting experiments on guilt and cooperation are underway, and it wasn't hard for me to track down some examples: see here and here for starters.
To me, the most interesting question about the emotions is why they so often conflict. Why do we experience simultaneous or near-simultaneous love & anger, lust & guilt, or curiosity & disgust? In evolutionary terms, it seems like it would be a lot more productive for us to have a one-dimensional emotional system that simply ranks things from "I really hate this" to "I really like this." If a person alternately inspires you and drives you crazy, it seems more productive to say "I can take you or leave you" than "I can't live with or without you."
The best explanation I can think of for conflicting emotions is that they guide us to corner solutions. Under certain conditions, moderation is the worst choice. If you have dated someone for enough time to really know each other, it is usually wise to either get married or break up. But this can't explain why you would keep feeling strong conflicting emotions for a long time, instead of embracing one and moving forward. And there are a lot of decisions where we feel conflicted even though a corner solution seems patently foolish. Your love and anger for your wayward teen-ager urge you to either unconditionally forgive or irrevocably disown, but the sensible course lies in between.
In the end, I suspect that our conflicting emotions are just another example of the myopia of evolution. Evolution never asks "What is the best overall package?" but "How can I tinker with this package to make it better"? Suppose you start with a solitary primate that feels lust. If conditions change to make group cooperation more important, he is less likely to fight with his fellows if he evolves a sense of guilt to check his lust.
An old joke says that a giraffe is a horse designed by a commitee. But the joke's on us: We look and feel like we were designed by a committee too.