I just realized the difference between thinking and insanity. Nothing! Absolutely nothing.
What do we perceive as the first sign of an insane person? A person that talks to him/herself out loud.
Thinking is basically talking to yourself in your head. It's the same thing.
This is in regards to 99% of thoughts, not the 1% that you do when you're actually solving something or doing something practical. But even then, if you're in the moment of doing it you aren't thinking, You're doing.
Think about it! Or don't.