It has been a long time since I last riddled...

I came up with this one a few weeks ago, I can't let Jon have all the fun.

What flies, yet never soars?
Slips through your hands to be never more?
Mostly lost, yet sometimes found,
When made up, you still lose ground.
Turning it back is a fool’s attempt,
In many ways it could be better spent.
On your side and at the end,
What do we wish to have the most of to spend?