They all say to trust your heart, to follow your instinct, and to do what you feel is right.
But what they don't tell you is that these things usually don't pay the bills–passion projects rarely start out as money-making ventures.
The passion is probably the $50 million company, but if you go broke before you get started, you'll stunt your ability to get there sooner.
The answer is to take a day job, work nights, work the weekend, and just generally do the "boring", non-glamorous work so you can pay the bills and reduce stress and pressure to make bad deals early on.
Reducing stress and pressure also has the added benefit of allowing you to operate more creatively which typically will have better long term payoff as well.
It's hard to get a second (or third) job! But almost nothing can beat hard work and commitment to the task at hand.
Do that and you'll be in great shape.