I have found that there is something innately calming about sucking something solid, whether it be a thumb or a paci. I actually prefer the intensity of the feeling I get when I such my thumb, probably because it allows for no movement at all and therefore is a more perfect medium in that way; however, my nails (even when trimmed) tend to cut my tongue, so I go with a paci.
I have a Nuk-7 silicon paci. (I have a Nuk-7 latex too, but it collapses too easily, so I pretty much stick to the silicon.) I pop it in when I go to bed and I go somewhere...else. If my eyes were open, I'd say they were rolling back into my head; it's like that. I just know I am away. Some nights it stays in all night; some mornings I need to hunt the blankets for it. Either way, it comforts me.
My daughter will be home from college for the summer soon and I'll have to stop using it for a few months, as I sleep with my door open because of my cats. I'll miss it.