Either by the trials themselves or by illuminating revelations. Trials and revelations are what it’s all about.**
(Joseph Campbell)

Whatever the reasons change comes, when it does, there seems to be three Events that instigate change: Contact with outsiders, Significant events, and Epiphanies.^
(Alex McManus)

The Teacher announces:

For everything there is a season, and a time for every matter under heaven: a time to seek, and a time to lose; a time to keep, and a time to throw away […].^^

The list is a much longer one, recognising life is often experienced most fully between apparent opposites. The largest of these may well be doing and being, the inner world and the outer.

What we find between the apparent opposites is the life of the protagonist, here described by Robert McKee:

We give ultimate value to those things that demand ultimate risk – our freedom, our lives, our souls. This is far more than an aesthetic principle, it’s rooted at the deepest source of our art. We not only create stories as metaphors for life, we create them as metaphors for a meaningful life. To live meaningfully is to be at perpetual risk. […] If, should the protagonist fail, life would go back to normal, the story is not worth telling.*^

I make no attempt to tell you what this protagonist life means for you. It is profoundly unique to every person; I only know it’s there to be discovered and expressed:

That’s why they always have blank pages at the back of the atlas. They’re for new countries. You’re meant to fill them in yourself.^*

(*I had Limahl’s Never Ending Story playing in my mind as I wrote.)
(**From Joseph Campbell and Bill Moyers’ The Power of Myth.)
(^From Alex McManus’ Makers of Fire.)
(^^Ecclesiastes 3:1, 6.)
(*^From Robert McKee’s blog: A Little Risk Goes a Long Way.)
(^*The BFG in Roald Dahl’s The BFG.)