Last night I was reading Ender's Game, which means that I'm way behind the times, since everyone else seemed to read it in high school. In the book, at least as far as I've gotten, the military leaders set up an increasing ladder of challenges for Ender. Each one is designed to be the exact difficulty that Ender can handle without breaking. I thought about how nice that must be.
It's good to have challenges in life. People think they want the easy life, but when they actually get it, no one ever wants it for long. Our entire existence is based on a series of ancestors who have pushed through very difficult challenges, many of which probably pushed the boundaries of their abilities. Overcoming challenges is very literally in our genes.
Ender got perfect challenges delivered to him. That's an ideal situation. In school we get challenges, but they're calibrated for a body of students, not an individual student. The likelihood of a school challenge being the appropriate difficulty for maximum growth is very small. If you have a good boss and are in a field that requires skill, your job might provide an appropriate level of challenge. If you're independent, you have to create your own challenges. Even if you're being challenged at an appropriate level in one area, that leaves all of the other areas of life up for grabs.
In other words, it's up to you to create your own challenges in life. I don't mean that you should cut off your leg so that you can experience the challenge of learning to walk with one leg, but I mean that in order to grow as a person, you have evaluate your options through the lens of determining what will challenge you at the right level.