A most excellent article on Entrepreneur gives many good reasons for quitting your day job. The best points made in the article have to be the death of the American dream and theres more to life than money. Those two points I definitely agree on. The amount of your salary will not determine your happiness in the long term because the more you make the more you spend needlessly.
Then the other problem with a salary is that you become accustomed to a certain way of spending lifestyle yet the next rounds of layoffs and cuts can leave you jobless or living below current lifestyle spending. People with lots of money are used to a way of life bought by their current income. Here is the myth of the American dream and its subsequent downfall: accustomed to spending a lot of money people are totally helpless in the face of losing current job or salary cuts.
In the next 20 years we'll probably see more and more jobs replaced by technology.
The second best point made had to do with salary unrelated to happiness. Think about the more you end up spending on mortgage, car, repairs, gadgets, fashionable clothes, and entertainment. Does this all make you happier in the end? Probably not.
Unfortunately, people get caught up in the Lifescript ideology once a legal adult. Go to college, get salary job with benefits, get married, and have family, and have enough for retirement. Why not just skip some or all of these Lifescripts? Its an outdated ideology anyways much the way family values and flat-Earth are outdated. You could end up saving a ton of money to spend on things that actually matter to you. Maybe instead of simply existing you can actually take the time to follow what matters to you.
Indeed, quitting my day job is a fantasy for me. Coming from a "working-class" background I have a fear of uncertainty and little confidence in my abilities (whatever they may be). But perhaps I can figure my way out of my predicament.