Doing what you love for a living sounds nice, until you get tired of it.
Some of us have hobbies to take our minds off of our cares and worries. We engage in these hobbies when we want to, for as long as we want to, because we want to, and that gives us a certain freedom that helps us deal with life’s stresses. Now imagine having to drag yourself out of bed and do it at a certain time, for as long as your boss/client requires of you, because you have to in order to pay the bills. Kinda kills the magic, doesn’t it?
Sometimes, we have days where we just don’t feel like engaging the things that we usually enjoy. Regardless of how much we might enjoy something, if we have to force ourselves to do it when we’re sick, tired, depressed or otherwise not in the mood for it, it doesn’t help anything. It actually ruins the feelings of freedom and joy we usually get from it.
Also, depending on what our passions are, they might not turn out the way we imagine they would in the professional world. Take writing, for example: there’s this myth that writers work comfortably at home, working the hours they want. In reality, it’s not so easy to make a comfortable living as a freelance writer. You don’t get to just write about whatever you want, as there are certain niches that pay more than others. And if you’re trying to write and sell a book, you have to write something that people will pay to read (and you still have bills to pay as you’re writing it). Musicians have a similar dilemma. If you work under a record label, you don’t always have creative control over your songs. If you’re trying to make it as an independent artist, you might have trouble making ends meet while you’re chasing your dreams.
There’s a good reason why we keep business and pleasure separate: the business spoils the pleasure.