One day you realize that you only have x days on this earth and y of them are already gone.
You don’t want to waste any more of your remaining (x-y) days refactoring the same poorly written crap for the eighth time, answering the same 84 inane emails, drinking the same lousy coffee, looking at your watch through another pointless walk-through meeting, and listening to the idiotic pontifications of a boss who you would never talk to in a million years if you weren’t here.
You know you can do better. You know you have it in you. You know you can make a difference. Then you know you “have” to. So you get out your calculator, work your finances, and when you have it all figured out, you turn in your notice and enjoy the best day of your life.