Threes and Sevens

I was just reading a pdf of the autobiography of Nikola Tesla.

In it, he mentions a need to do repeated actions a number of times divisible by three.

‘s beau Damon has mentioned a need to do such things in sets of 7. (Either Kendra Myers or Mary Kraft mentioned having the same need for 7).

What is this about? What on earth is this compulsion?

A form of OCD no doubt, but… weird.