You write "you become a leader in your field, company, group, etc." but that's not really thinking outside of the box, is it? There are those who create entirely new fields, without being a leader. Some of them aren't even known for their work until after death, so can be called 'leader' only in a way synonymous with 'pathfinder', and not at the top in some sort of hierarchical sense.
It also sounds like you define your life around your occupation. What happens if someone wants to be the best parent they can be? Or the best neighbor? What does it even mean to be the "top" in that field?
You write "due to not being challenged enough in life" and I look in disbelief - change jobs. Become a surgeon, or concert violist, or bush pilot, or any of thousands of challenging jobs that have nothing to do with what you do now. Why stick with the same field to find challenges? There's more than only vertical growth. Or learn new hobbies. There are many so-called 'skilled junkies' in the world, and I've not heard of anyone who has mastered everything. You mentioned 'well-rounded', so I assume that's what you are talking about as well, but skills acquisition doesn't need to be part of a competitive world-view. It can be for enjoyment only.
I even find odd your concept of worrying about giving up when it appears to get too hard. If the goal is breath-taking-ness then choose routes to maximize that. There's no need to manufacture and reach a specific unwavering goal for the side-effect of getting that breath taking feeling.
The classical models of conflict are "man against man", "man against nature", and "man against self." The competitiveness you talk about I think only refers to the first of these. I long ago decided to avoid those, and focus more on the latter two, so that I'm doing the things based on my own scale, and not always ranking myself against others.
As an example, in my 30s I started doing a lot of partner dances. I deliberately did not advance past a certain level. I found as I got better I was having less fun dancing with people locally. If I got much better still, I would only be able to enjoy dancing by going to regional dance events, and what I wanted from dancing was to be social with local people.
I don't think I was trying to be the top local dancer. I don't think I was trying to be the best of friends with people. I didn't organize dance events, etc. I was enjoying myself, enjoying being part of the scene, and learning new skills in the process. I don't see how that sort of continuous self-improvement is strongly connected to being a leader of any sort.
If you are competitive then striving to become the best you can be comes naturally. Helping others on your way to the top also comes naturally as to make it there you have to have the help of others since it cannot be done alone. The good life is relative to ones goals in life, thinking outside of the box goes against the status quo as it is a different way of doing something that has not been done.
Normally on your way to continuous self-improvement and helping build up others around you become a leader in your field, company, group, etc. without even thinking about it. No need to try to be the next so and so, it is better to be yourself and enhance your potential at a pace that keeps you challenged and on your toes. The world is better off with unique leaders, versus people not being their genuine self when trying to lead change and improve things for people around them.