Especially on short putts, listen for the ball falling in the hole, rather than trying to watch it.
This will build confidence and make sure that your stroke is not adversely affected by lifting your head, which changes your posture in mid-stroke.
To begin with, listening for the ball to fall in the hole will take some courage which will be rewarded by sinking more putts.
Unfortunately I m legally deaf, but with hearing aids and I still can’t get the reward of that successful sound. Never the less, I constantly practice your Bible the Fundamentals of Putting. I have prepared a check list, typed and laminated, that I carry with me. My Summary version of your book Summaries.