I cannot take melatonin, it makes me suicidally depressed. I have tried on two separate occasions, and it was extremely unpleasant. I don't know why it does that to me, except maybe it has to do with not having enough serotonin in the first place, and melatonin is the opposite...?
Or maybe it's the vitamin D deficiency? My doc just had me tested for vitamin D levels, and I was insufficient (I had 16 and you're supposed to have 30-100) so maybe it is related to that, but anyway...
I lay there in bed for at least an hour every night of my life, even as a little kid, my mind just doesn't shut off, and then I can't go to sleep until I'm warm enough.... and... and.... oh well. It's just always how I've been, unable to shut off, and hard to turn back on in the morning too. I've always thought that I would have done so much better in school if it had started about 2 hours later 
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{the avatar is a Claude Monet}