Obviously some of us dont have the luxury.
However probably one of the only things my dad said that I really took to heart was this:
"When you are young, you work to live. You work to pay your new bills, to pay off student loans, to eat, to get by. As you get older, you work because it is what you love to do. While not everyone does this, it should be your goal."
Now if you make 400 million dollars a year, you have enough cash to do whatever the hell you want regardless of whether you like the job or not. Most of us dont make it to that level, and so we must decide between the job that pays 30K where we cant wait to get to work, or the job that pays 40K where we dread the morning. I personally was happier as a cook in a diner making about 17K/year than I would be as a .....say marketing rep making 40K behind a desk. I can honestly say I would choose the cooking job.