Many years ago, at the end of several days that turned into night, which then bled into the morning, I sat persistent in meditation, watching the breath, with a stable rock-like concentration until i arrived at a sort of strange peak experience whereby this new sudden sensation was of a rope of energy being pulled or emptied through the crown of my head, while internally i watched the pouring or shimmering movement of a wide water-like dark grey and silver 'veil'. It went on like that for some time and when it stopped I had to open my eyes for the first time in many hours - because I now felt totally emptied of all bodily sensations - so much so that right away I passed my arm in front of me, not at all sure i would even see it. It's funny, I know. My arm almost like a small cushion in zero gravity floating past a camera on the space shuttle.
The next morning I noticed right away how I felt really quite terrible, like each part of my entire body was full of weariness and a sense of discomfort. Something else that I noticed, for a few weeks following the odd experience that night, I'd find myself walking and looking at the face of a random stranger and being able to see something which I can only describe as seeming like ancient pain.
A few years ago, just as friends, I told my wonderful former therapist, who is also a devout Buddhist, about the peak experience, the sense of emptiness and the arm check, and i went into special detail about the awful feeling the next morning. She made a face in sympathy and said, "That's never how I feel. I always feel really light and energized and happy the next morning after meditation!
I told her that's because you're doing it wrong and we both had a good laugh.