There is really only one thing that old people know, which young people don't: and that is, that some things heal over time, and some things don't, and that there is no way to know ahead of time which is which.
I first started walking in Forest Park when my knees were bad. It's a huge city park, many miles of the last barrier of forested hills that make the Willamette give up on finding its own way to the sea, and flow north into the Columbia instead. There were a few wandering dirt roads here, before it was made a park. They have become greenways now, healed over with grass and fern; usually one of the old wheel ruts has become a hiking path, and only there does the beaten earth still show. It doesn't take long, in this mild, rainy country, for a road to be reclaimed by the green world.
I took to walking there because the trails were old roads, and roads, unlike trails, usually limit themselves to a 3% grade, which my knees could handle. When I was a college student I went hiking in the Olympic mountains in Washington state, low mountains but very steep up and very steep down, where every couple of miles you come to the crest of a new ridge and a new world opens in front of you, a sort of miraculous miniature Himalaya. The lure of one more crest and one more world was irresistable, and I gimped home in agony, one knee so traumatized that I couldn't bend it. It's never fully recovered, and when it's bad, and I favor it a lot, the strain tells on my other knee. I doubt that in this life I will ever be making a twenty mile hike, again.
Anyway. I will take you there, when you come, and we'll walk under the douglas firs, and you'll tell me about the trees of your own country. There's a clearing we can reach by a narrow, barely-visible path. Along the way we'll pick a couple handfuls of blackberries, and then we'll sit on the long yellow grass of August and look down at the distant railyards, and the freighters on the river. We'll eat the sunwarm blackberries, chewing thoughtfully on the seeds. We'll talk about many things, but you won't talk about young friends drowned, or the slow path to exile, and I won't talk about love.