I learned to not obsess about gear and gear weight so much. After hiking enough miles on a given trip, a few ounces here or there don't matter. Note, however that's after a lot of obsession last year to bring things down to a moderate (light, not UL) base weight.

A related item, I learned not to obsess so much about having the exact and correct set of gear for a particular trip. Assuming safety and basic comfort are covered, it's not a problem to improvise or live without stuff. For example, mini-scissors on my mini-pocket knife turned a black plastic garbage bag into a fine (if not breathable) windshirt at need.

On trail "menu": I did learn some minimal set of recipes I can create from what's available in a medium sized trail town store, but also that I don't need a ton of variety. If I can vary my breakfast shake from chocolate to vanilla and eat a different brand of trail bar, that's "variety"!

I learned that I can comfortably cowboy camp when conditions warrant so, for example, I'll likely just bring a poncho and very lightweight bivy for a Grand Canyon trip this coming March.

I learned that --- for me at least --- an MP3 player is worth carrying on a long solo trip.