Garrison Keillor once said that intelligence is like 4-wheel drive. It only allows you get stuck in more remote places.
It's been said enough that the smarter you get, the harder it is to either find happiness, stay sane, or both. Sometimes you simply get tangled up in your thoughts by being even slightly intelligent because normal everyday functions suddenly become infused with potential meaning.
You question more, you become overwhelmed with the directions things can take, you try to follow chain reactions in the world and find that they don't really end, ever. Some people would say that insanity in light of intelligence is a blessing, a deliverance. For others, that's the end to avoid, to stay just above water. And for even others, ignorance is bliss.
If I am intelligent at all, old Garrison is onto something.