Inner growth is defined as many things: life lessons, wisdom, knowledge, and evolution, to name a few. It's typically acquired as a result of life experiences, and usually those particular experiences aren't very pleasant. Humans seem to be wired to learn through pain, which I guess makes a lot of sense when you think about it. After all, if everything was hunky dorey all the time and we felt good about all aspects of our life, why would we want to take a chance on ruining all that just to learn something?