What is rest?

I've been thinking about what it means to let the mind rest, which is what we do in zazen (sitting meditation). This comes with the realization that I don't really know how to do this (even after 9 years of practicing). I realize that I tend to dream a lot (as many of us do), replaying snippets from the past, speculating on the future, planning, making lists, etc. When I try to let all of that go, I tend to get sleepy. One thing that this tells me is that I'm escaping in two primary ways: working on something, or sleeping.

I'm not being all that judgmental here, though it sounds like it. I think many people are in this situation without really seeing that. I'm trying to see what's really going on here. My lifetime M.O. has been to distract myself from difficult emotions or situations either by working or by sleeping (or otherwise shutting down, if actual sleeping is not possible). Work can be defined pretty broadly, including that planning, strategizing, speculating, etc., that I can do endlessly on the cushion if I don't stop myself.

The problem is that when I do manage to stop myself, I get sleepy. And what I realize about that is that this is another attempt to escape the present.

So, what does it mean to let the mind rest? Just to sit still? To notice what is happening around me, to appreciate the morning, the sounds of birds, the light on the carpet in front of me, the comfort (or lack of it) of my body sitting. I've been trying to bring this mind of zazen gently to noticing how much I try to work, sleep, or otherwise escape, while I'm on the cushion. Just to notice, not to judge.

This is still not easy for me. I will keep working on it, though. Once in a while I find myself in equanimity, just resting, just sitting still. It's a nice place to be.