The reasons entrepreneurs fail are as varied as the entrepreneurs themselves, of course.
However, there is one common denominator: They almost always move too quickly.
Now let me stop here. I am not saying you need to take every possibility into account before you do anything. That's just silly. You can study and study and study some more and still decide that you are not ready.
If you go that route, you never create anything.
Or, if you finally get around to pulling the trigger, you may find it is too late. Someone could have beat you to market.
I am a HUGE fan of acting over thinking. The only way you know anything for sure is by taking action.
But, and it is an equally HUGE but, the action I am advocating is taking small steps toward your goal.
If there is a formula the most successful entrepreneurs follow, and I think there is, it looks like this.
1. Start with desire. You find/think of something you want. You don't need a lot of passion, you only need sufficient desire to get started. ("I really want to start a restaurant, but I haven't a clue if I will ever be able to open one.")
2. Take a smart step as quickly as you can toward your goal. What's a smart step? It's one where you act quickly with the means at hand. What you know, who you know, and anything else that's available. ("I know a great chef, and if I beg all my family and friends to back me, I might have enough money to open a place.") You make sure that step is never going to cost more than it would be acceptable to you to lose should things not work out. And you bring others along to acquire more resources, spread the risk and confirm the quality of your idea.
3. Reflect and build on what you have learned from taking that step. You need to do that because every time you act, reality changes. Sometimes the step you take gets you nearer to what you want ("I should be able to afford something just outside of downtown"); sometimes what you want changes ("It looks likes there are an awful lot of Italian restaurants nearby. We are going to have to rethink our menu.") If you pay attention, you always learn something. So after you act, ask: Did those actions get you closer to your goal? ("Yes. It looks like I will be able to open a restaurant.") Do you need additional resources to draw even closer? ("Yes. I'll need to find another chef. The one I know can only do Italian.") Do you still want to obtain your objective? ("Yes.")
4. Repeat. You take another small step and see what you learn from that one and build off that. The process continues until you achieve your goal, realize it can't be done or decide you want to do something else.
As you can see, with this approach you are constantly moving toward your goal. But because the steps are small, it is hard to get too far off track, and you end up risking far less.