Restless longing seems to come up often in my conversations - probably because I've been asking people, "Are you full of restless longing?" One friend says he wants to travel more and more every year. I said, "Are you full of restless longing?" He replied, "Yes, at my back I always hear/Time's wingèd chariot hurrying near."
My sister said we have less restless longing as we get older. But those irritating bucket list books full of things to do before you die suggest more. I wonder if restless longing is a gender thing, with the Y-gene carrying more restless longing than the X - but probably not. Restless longing is a state of dissatisfaction. It's nice to feel more satisfied and peaceful, but restless longing keeps us from becoming complacent and smug.
There's even a colour called "restless longing". It's a fresh, bright green - suggesting a touch of envy. You can see it here: http://www.colourlovers.com/color/BAF7BF/restless_longing.
Mostly, I figure longing is just lounging without "u"
I move up and down the continuum between restless longing and contentment. Sometimes I lean more towards Andrew Marvell:
"Let us roll all our strength and all
Our sweetness up into one ball,
And tear our pleasures with rough strife
Through the iron gates of life:"
But not often enough. Maybe I am full of restless longing. Are you?