It's impossible to tell yourself what things will be like when you're older, but we certainly want to try and reach out to our younger selves these days.
Twitter user @nicksonpt2 invited the discussion when they tweeted:
And people had quite a legion of different answers, starting with cartoons we all know and love:
The truth about adulting:
The other truths about adulting:
How to treat others like humans:
That everyone has a sly sense of humor:
And of course, the things we wish we'd known all those years ago: