One that effectively says stop what you're doing and come over here when your concentration is wavering.

They'll just fall back into place when your concentration wavers.

He admitted that his concentration during the game wavered.

There was a job to do and he was a professional; his concentration could not waver.

The old man's stamina was amazing, and his concentration never wavered.

He knew she must have been shocked, but her concentration did not waver.

If your concentration wavers for just a second, you're going to miss something.

And if her concentration wavered, even for an instant, there was yet another image.

Mayo's concentration didn't waver from the images moving before his screen.

But now as they approached her again, her concentration wavered.