In this case, I would say they mean take a job doing something you enjoy but aren't so invested in that you will resent doing it the way your boss wants it done or feel like you lost something when you get home and don't want to do more of it for fun.
Some programmers write code at work and then do side projects on top of that. Other people enjoy knowing a little code, but would find it burdensome to write production quality code everyday. For them, programming is a hobby. Other people are content to program for their job and then leave it at the office and stop there.
People who have a hobby they love sometimes find their enjoyment is completely ruined if they try to turn it into a business. Loving something on weekends and evenings doesn't necessarily translate to being able to do it happily all day, everyday for work when other people are calling the shots and telling you how to do it.
Some programmers write code at work and then do side projects on top of that. Other people enjoy knowing a little code, but would find it burdensome to write production quality code everyday. For them, programming is a hobby. Other people are content to program for their job and then leave it at the office and stop there.
People who have a hobby they love sometimes find their enjoyment is completely ruined if they try to turn it into a business. Loving something on weekends and evenings doesn't necessarily translate to being able to do it happily all day, everyday for work when other people are calling the shots and telling you how to do it.