This is an interesting question and one that should be asked well prior to ever diving into the world of entrepreneurship. Far too often, this is a question an entrepreneur asks when already knee-deep in starting a company with a basket of problems and growth issues.
My first piece of advice is to define what it means to you to be successful. In business and in life, we're constantly weighing our options for going in one direction over the other. For instance, you may be in a situation with a high-paying job when an opportunity presents itself to start a new company in a new market. Sure, you can stay at the high-paying job and maintain that sense of security or you can take a chance with the business venture. If you're seriously considering starting the company, then you should define what it means to be successful versus staying in that cushy job. If it means that your business is a failure unless you start the next Instagram or Pinterest, then chances are you should stay at your current job. If, on the other hand, it's a success if you start the business, generate revenue, gain customers, prove the model and make a living for yourself, then that's a different story. My point is that you want to set a reasonable expectation for what success will be for you so you don't find yourself hitting your head against the wall wishing you had done things differently.
My next piece of advice is that you really have to want to experience the journey as an entrepreneur. Most successful entrepreneurs with whom I speak say they had no idea that their venture would be such a success, they just hoped it would work. The great success stories just kind of happened. Sure, it takes a ton of work and planning and you want the right resources in place, but sometimes it just happens and you can never plan for that. My message here is that you have to be willing to accept the bad days (there will be many) as well as the good days in order to jump into entrepreneurship. It's a lifestyle, and rarely a quick route to financial success. Even the Pinterests and Instagrams of the world went through many growing pains, and it took a great deal of talent and hard work for them to get to where they are today.
I hope you find this guidance helpful. Remember, you have to define what success is for you (it's different for everyone) and you shouldn't expect things to happen for you unless you put in all the energy it takes to be a successful entrepreneur.