If steady sounds like soft to you, notice who actually holds a room. It is not the one who goes off first.

What the research says

In an eye tracking experiment with 43 novice dart players, deliberate self talk helped people hold their attention and their performance under distraction and mental fatigue, though how much it helped depended on how depleted they were. The words you use on yourself do some work. It was a sports task with a small sample, so do not lean on it too heavily.

Strength of evidence: one line of research. A single study, or a theoretical account.