In what way is egoism rational? I would point you at this answer of mine to a different question: https://philosophy.stackexchange.com/a/17541/9166
From that perspective compassion is a deep, often unconscious, genetic force, which we actively fight against when we are focussed on ourselves. (To me, this is an inherent flaw in the concept of economics, and especially male gender roles.) So I am discarding this aspect of the question.
The imperatives that come to us genetically do not always make us happy when we serve them or unhappy when we don't. To a large degree, I think this has a lot to do with biases we lay on our emotions. https://philosophy.stackexchange.com/a/18324/9166
From that perspective sometimes we are driven by positive forces that we have colored negatively. Our built-in reactions are just misaligned with our psychological labeling of them. We are happy in some abstract sense, but just not in a way that we are 'happy with'.
Attachment is also an issue. Driving forces become habitual, to a degree where they sometimes just pervade our thinking inescapably and we lack choice.
Say I am a happy 'geek', my energy (consciously or otherwise) comes from being competent. When I try to do something ungeeky, like fall in love, I am still driven to display my competence at the cost of admiring subtler things, and I make things hard for myself. At the other extreme, If all my happiness unconsciously comes from empathy, and I choose the wrong kind of husband, I may choose to try to understand someone who cannot understand me, instead of protecting myself from his violence.
Attachment can also become obsessionality: the fear of challenging attachments, or the fear of change outright can have more power than the pursuit of happiness. Attachment is a positive force, in a lot of situations, but it can prevent movement forward that would sacrifice what we currently have, even if we honestly and logically do not value what we have very much.