I think part of what it means to be happy is to love what we do, moment to moment. That we don't always begin with an overarching love for what we do. Instead it is sometimes the result of conscious decisions to do things a certain way.
Because loving what we do is only partly about the thing. It is sometimes about how we do it. And so any role or project can be more fun or rewarding, depending on perception, depending on attitude, and depending on approach.
In this way I find that love is as much about what is cultivated as it is the things we love at the outset. That it is as much a result of choice as it is the things we are passionate about. And more than that, what we cultivate become stable buffers against passions' turning tides.