yeah, everything GGB said. ('cept, I thought i'd get yelled at if I didn't say more about 'feelings' in there. ;)). I was going to say "peace" ...but that isn't really quite right. even on a casual joy-ride on a calm, clear day, you're always subconsciously "on your toes", never truly relaxed until its over. Then I have the overwhelming urge to light up a butt, and take a nap. (hmm...whats that sound like?)
but anyway, yeah, there's this "zen-like" groove that you get into, when everything is right.
Now, don't get me wrong--I don't want to sound like I have this overly-romantic image built up in my head. I've spent enough time in the cockpit to know that it ain't all peaches 'n cream, and there have been plenty of times when I've wanted nothing more than to get my a$$ back on the ground. but mostly...not.

and speaking of touching the face of God....(if you're into that sort of thing...)

Oh, I have slipped the surly bonds of earth
And danced the skies on laughter-silvered wings;

Sunward I've climbed, and joined the tumbling mirth
Of sun-split clouds - and done a hundred things

You have not dreamed of - wheeled and soared and swung
High in the sunlit silence. Hov'ring there,

I've chased the shouting wind along, and flung
My eager craft through footless halls of air.

Up, up the long delirious, burning blue
I've topped the windswept heights with easy grace

Where never lark, or even eagle flew.
And, while with silent, lifting mind I've trod

The high untresspassed sanctity of space,
Put out my hand, and touched the face of God.