Several months ago I went through my first insight cycle. I tend to drop into interesting mental states after around 30 minutes of continuous meditation if I've been meditating regularly. At the time, I was doing up to 45 minutes of meditation per day.
It is default human nature to block out the nastiest aspects of life. The meditation I was doing removed those blocks, dropping me into a vortex of suffering Daniel Ingram calls the Dark Night.
My Dark Night lasted a few days. It ended when I let go of the idea the world should be a certain way—that I should be other than what I am.
I remember the exact place I was the instant my mental shift occurred. I was walking barefoot on a little hill. I walked up that hill with my problems. When I walked down they weren't my problems anymore. They weren't even problems anymore. They were just facts.
For most of my life, I have carried around an image in my head of the man I should be. I worked hard to become that man. My belief I should be someone I'm not was instrumentally useful, but it also caused me chronic suffering.
My experience on the hill permanently changed how I related to the world. My belief I should be someone I'm not shattered completely. Nearly a year has passed, and I have not reverted to my previous default state.
This isn't to say I don't suffer anymore. I still suffer feel cold, hunger, embarassment and social awkwardness. I think to myself "I am embarassed I said such-and-such thing" but I no longer also think to myself "I should be someone who does not say such embarassing things". I try to prevent bad things from happening but I do not feel the world should be other than what it is. There is no "should" in reductionist material causality.