One of the reason I chose to be an entrepreneur was that my ability to learn is limited only by me. I'm regularly learning new things on a very broad range of topics from entrepreneurship itself, cryptography, distributed systems, marketplace building, people management, sales, marketing, economics, and many more. But, here is the thing... I don't feel like I'm making progress towards complete knowledge.
No, actually the very opposite is occurring. I, often, feel as if I have newer questions I didn't even think to ask myself when I receive new information. The process goes something like this: "Oh, looks like I need to solve this problem. Let me look for a solution", "Wait, why did they choose to solve the problem in this way?" "Okay that makes sense, but there are still some gaps. Can I do something different that may solve this problem differently?" "Does this solution actually accomplish what I set out to achieve?" "What else can I do to make this better? What's good enough for today?"... and the cycle goes on and on.
If you are someone who likes clear cut answers to things than maybe you should stick to mathematics or physics, because outside of those fields almost every answer has a trade-off and can be questioned to infinity. But, see that's actually great! If most things can be questioned, it means that there is room for improvement or a different set of tradeoffs can be made to make a unique solution. If you find yourself in a place of more questions than answers after serious efforts, it means you are operating in the frontier and that's an exciting place to be.
If you are grappling with something and you feel as if the answers are not coming to you. Just step back for a second and identify whether you are even asking the right question(s). Often times people have tried answering these questions in the past with some degree of success and the answer may exist out there but you may have to reframe yourself first. And sometimes... destiny dictates that you must be the one to answer this question for the rest of the world.
Also, when pitching investors I don't know whether they want me to pretend that I have all the answers to all the questions in the world, but I feel like the intellectually honest response would be to say "I don't know, but here are the three most important questions that I'm facing right now around this problem" I've come to realize that I become skeptical of people who believe that they have the sure-fire answer to most things.
If you ask my mom, I wouldn't let her sleep through the nights because I always had "one more question." But, I'm sure every parent feels this way... maybe my parents just never killed that curious kids appetite for knowledge.