A friend of mine started a business because he thought he could make money. He had no particular interest in that business. Didn't love the industry. Didn't love the product. Didn't love the work. Did think he could make money.

And he did, until the going inevitably got tough, and he gave up and quit.

...A 2014 study published in the Academy of Management Journal found that while most people, and most theoretical frameworks, assume that entrepreneurial passion drives entrepreneurial effort, research shows the reverse is also true. Entrepreneurial passion tends to increase with effort: the more work entrepreneurs put into their startups, the more enthusiastic they tend to get about their businesses. As they gain momentum, gain skill, and enjoy small successes -- even if those "successes" only involve ticking off items on their seemingly endless to-do lists -- their passion typically grows.