Men in their 40s, what’s one piece of advice for men in their 20s?

When things are great, even small things like a cup of coffee with a friend or a quiet morning, take a minute to say to yourself, "this is really great." Say it out loud. Years later you will realize those moments are as good as it gets, and if you don't mark them they just disappear. Bad moments stick around in your head regardless, but the good ones need to be memorialized.