Sometimes people pick up pet worries that they'll entertain themselves with and that was my big one. So as far as thinking about what that means, one of the definitions of insanity is that you lose your ability to communicate to anybody because your frames of reference have become so different from the rest of the world that you can't communicate anymore.
There's also something that is often mistaken for enlightenment which is a kind of insanity. Often, people will have some kind of weird experience which is quite abnormal and think, "Oh my God, that's it, I understand everything" because they start seeing things in a very weird way and think that's how enlightened people see things as well.
I think real enlightenment is total sanity, a kind of acceptance of what actually is. It does involve a kind of different way of looking at things. As I've done this Zen practice for years and years, I've acquired what I realize is an almost upside down view of life compared to what most people think, which is just what I used to think it was too. It's not really an insane view, at least I hope it's not.
You can't function in society if you don't involve yourself in the fictions society accepts about time. But you do so with the understanding that you're playing a game.