He would experience all of the mistakes, regret, pain, suffering, and all that bad stuff, but he will also experience all of the love, joy, laughter, and all the other good stuff. In the end, one of his single lives still went through the same motions of all of his other lives together, just at a smaller scale.

That is how we mature in life. We learn and grow from our mistakes and accomplishments. Our pain and our joy. You can, as many do, see life as just one big shithole of pain, but you would still be missing out on another side of it.

That's at least what I got out of the story. I thought it was lovely.