Emergence
When new things are created, a strange thing happens: You might start with an idea or a problem but you don't know all that much about it. As you and maybe someone else proceed on this path, however, things are starting to make sense – emergence.
The first reason I am addressing this presumably obvious thing is that it is usually not obvious in the beginning. I am generally a pessimistic person when it comes to new challenges and I never (truthfully) wrote "I like to work on hard problems" in a job application. And I think that the majority of people accept to work on hard problems because of a higher cause than just for the sake of it. But that means the problem is still hard.
The second reason is that while you are in the state of not knowing, it doesn't feel particularly pleasant because of the very fact that you don't know so many things. A typical theme when starting a new business: More problems than solutions, those "huge competitors" (that often turn out to be much more caught up in their own thing), questions from others that you don't know how to answer, no customers, plot holes.
Emergence is the process that takes place while you are focusing mental or physical energy on something. It can be accelerated through talking to other people, whether they are friends, peers, investors, co-founders, mentors, or just any person that might have a valuable view of what you are doing.
What I like about this process is that, eventually, there comes a point where it clicks. When I started DJing, there was a point where I knew that I was good at mixing tracks. I could hear it and saw it in my friends' faces. When I later moved to vinyl, it took a while again until that state re-emerged.
I experienced the same in the last company I worked at and again a few days ago when I finally got a full picture of the new company we are currently building.
Here's a bit of reality though: Emergence doesn't mean that things automatically work in a "good" direction by whichever measure you apply. It is very well possible to work on a particular problem for a long time, only to find out that you overlooked something important or ran on false assumptions.
A Heureka moment is a wild experience that makes everything that happened before seem like a shadow version of the actual thought. From there on, the only questions are about how to get the message out, how to turn it into reality, and not mess things up too badly along the way. But those problems are a lot less hard than not knowing the direction in the first place.