I strongly believe that you need the following to really thrive as an entrepreneur.
1. Be Passionate - like one of the earlier answers, you gotta love the process. But I'd also like to add that not only do you need to love it, you have to be passionate about it. This means that you get up in the morning excited to work on your business, dream of ways to make your business better in your sleep, and it's something that doesn't feel like a drag doing but where time flies!
2. Find the right timing (or luck) - Timing is always key in the industry. No point trying to build a company that either reinvents the wheel or in an industry that's dying. Find a market niche that you can either thrive in, or do well in.
3. Don't expect to take a road trip without a road map - I see a lot of entrepreneurs that jump into a business because they "feel" or have "heard" that it makes money. Instead of doing the proper market research and planning, entrepreneurs just "start" and hope to make it big. This is definitely not the way to go. Entrepreneurship takes a lot of time, effort, energy, and money (which we all do not have enough of), so why not do your proper research and planning so you know exactly what you're getting yourself into.
I am reminded of two quotes:
“Nothing in this world can take the place of persistence. Talent will not; nothing is more common than unsuccessful people with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. The slogan "press on" has solved and always will solve the problems of the human race.” - Calvin Coolidge
"I've missed more than 9000 shots in my career. I've lost almost 300 games. 26 times, I've been trusted to take the game winning shot and missed. I've failed over and over and over again in my life. And that is why I succeed." - Michael Jordan
Most recently I have learned that if one deal, one customer, is the difference between success and failure, then I don't have enough customers, and am probably doing something wrong in operating my business.