Know your aptitudes, skills, passions, and inclinations.
But focus more on the opportunities in the market.
Too many focus on what they enjoy doing, or a particular skill set, at the expense of the needs of the market.
They make a fetish out of their passions, and eventually become slaves to them.
Here's a hint: Let your passions serve you, not you them.
It's more important to learn how to spot a good opportunity - what I call, looking for oil - than to simply be out and about drilling for drilling's sake. Better to take the time out, assess one's strengths, look for wonderful opportunities and then apply oneself to the deep drilling required to make the pursued course a success. We don't know how deep we may have to drill before we hit oil in most cases. We don't know how many opportunities we'll have to look at before we find one we're willing to invest our blood, sweat and money.
1) A great entrepreneur can make great money in nearly every industry, in almost any economic situation. The reason why is because he is focused on the opportunity, taking a bigger-than-me approach to the situation. He sees the business for what it is - not for what he wants it to be or for what he can enjoy doing in it. He focuses more on the likelihood of finding oil, rather than the joy of drilling.
2) Once one has spotted likely ground, one must be willing to drill down deep. That is, one must have the capital, focus, persistence, and yes, an adequate supply of passion and other character-based resources to make the endeavor a success - IF he is to succeed. There's no guarantee that the spot drilled will yield any oil at all. But we've all heard the stories of men who've drilled within inches of major oil wells, gold mines, etc. only to give up a bit too soon before selling out. To succeed with principle # 2, we must have an accurate assessment of our available emotional and financial inventory.