Outside of the psychological stresses of entrepreneurship, I think the single thing that limits entrepreneurs the most is their imagination. This sounds counterintuitive, since entrepreneurs are by nature creative problem solvers, but like everyone else, the solutions that they can imagine are constrained by their life experiences.
One of the most important things that entrepreneurs can do to prepare to start a business is gather life experiences, in order to expand their ability to find problems to solve and imagine the solutions to those problems.
Imagine you're an average, starving artist who was magically transported to an alien world. On this world, you see paintings painted with an entirely new palette of colors, ones you have never seen on Earth. These colors defy our ability to describe or imagine them, because they have never been part of our experience. When you return to Earth, you bring those colors with you to the delight of your audiences. Your ability as an artist may not have improved at all, but all of a sudden your paintings have the advantage of novelty, exposing the earthbound audiences to colors they have never seen before that amaze them. You become a renowned and wealthy painter because of your ability to show your audiences something they have never seen before.
I have recently talked with a number of entrepreneurs who have had their dreams of building companies deferred because of the current economic circumstances. For very understandable reasons, they have decided to seek out gainful employment rather than try to raise capital and build a business in the face of our current uncertainty. Many of them are students, preparing to graduate from college and trying to reconcile their self-identity as an entrepreneur with their desire to get a full-time job.
My advice to them is to think of this time as an opportunity, not a curse. Many of these promising entrepreneurs have started businesses in predictable student-business industries solving problems like food delivery, housing subleasing, or travel and photo sharing. Most of them are excited to be "painters" and have great potential, but they have a very limited color palette to work from by virtue of their limited life experiences. It's no knock on those people; all of us had a very different set of life experiences when we graduated from college than we did at 30 or 40 years old.
There is plenty of time to learn to be a better entrepreneur, just as a painter will always want to hone her craft. Going into an industry and getting a "real job" only expands your life experiences and widens the problem sets you are exposed to. You'll find inefficiencies everywhere in the real world! The way things are bought, sold, marketed.
The technology and software systems underpinning all of these processes are full of problems begging to be solved. For the entrepreneur, it's akin to being teleported to that alien world, exposing your mind to a whole new palette of colors to consider painting with. This new universe of opportunities may be much more interesting than the things you had previously been exposed to.
When the timing is right to start a business, by all means, go start a business! Answer the call to adventure, follow your bliss, dare greatly, and go innovate. But remember that timing is everything and there's nothing wrong with expanding the palette of your imagination while cashing a paycheck before you get back to painting full time.