She wanted to tell him to stop wasting his strength, but could not summon the energy to do so.

Don't waste your strength beating on a door that won't open.

"I've wasted my strength going here and there when I could be using it for my son," she said.

She knew better than to waste her strength on useless effort.

Why do you waste your whole strength on such as he, when a couple of men can finish him in as many minutes!

"I'm certainly not going to waste my strength on the likes of you."

Perhaps he did not want to waste his strength.

Jason realized he was wasting his strength trying to carry her up the wall.

The people were going to have plenty to do: it was a pity for them to waste their strength beating one another.

To waste one's strength in anger is to throw it away before a time of true need.