Can't emphasize this enough. I've talked to countless people unhappy in their career that can't get out of it because of a family and an addiction to their current lifestyle. They continued to expand their spending as their income incremented, leaving them in a risk averse position.
The lesson I take from every conversation I have with these people is live simply and lean even as your income grows, and when you have that great idea or urge to try something radically different, you can.