A tiny pebble can literally wear you out. Figuratively, there are many little pebbles in our lives that can wear us down. Nagging little pesty worries that we can't seem to let go of.
"It isn't the mountains ahead to climb that wear you out.
It's the pebble in your shoe."
I've got a pebble in my shoe right now. I have to make an unpleasant phone call that I've been putting off. Maybe I'll go do it now and be done with it.
When I worked as customer service/repairs at an international company I started each day by making calls to our most difficult customers first. I never wanted those calls hanging over my head all day and tackled them while I was feeling fresh. Then I could call the more pleasant customers to chase the others from my mind and finally end the morning with good news calls. This is why I was always given the more difficult customers to deal with and why the owner of the company would not take any calls before noon. He knew that by then I would have things sorted out
