It usually is a sum of many things. It's always interesting to read how others found their path toward their passion. The final shot that led to my resignation from my lawyer's career was when I lost 75 000 dollars in my personal life.
Today, I see it as a blessing, though it made me go through very dark times. But, it has been one of the best things happening to me and directing me towards the right road in this game that we call life.
Remember that no matter what you're going through, it's only part of the learning curve. How you perceive things happening to you is the key. You can either let it bury you under the crap or make you rise like a king or a queen.