One definition of insanity is to do the same thing, day-after-day, expecting different results

To be mad is to feel with excruciating intensity the sadness and joy of a time which has not arrived or has already been. And to protect their delicate vision of that other time, madmen will justify their condition with touching loyalty, and surround it with a thousand distractive schemes. These schemes, in turn, drive them deeper and deeper into the darkness and light (which is their mortification and their reward), and confront them with a choice. They may either slacken and fall back, accepting the relief of a rational view and the approval of others, or they may push on, and, by falling, arise. When and if by their unforgivable stubbornness they finally burst through to worlds upon worlds of motionless light, they are no longer called afflicted or insane. They are called saints.

It's regrets that make painful memories. When I was crazy I did everything just right.

After my first few tastes I was pretty much hooked. I'd have dry spells, months without any or only piddling amounts of grace, but I never forgot about it or stopped wanting it.

We have an insanity plea that would have saved Cain

Having their feelings make sense is how people get their kicks.