I found this article interesting and easy to understand.
I personally can't be bothered to use "hard numbers" and HR monitors / watches all the time so I've learned to train and race mainly by feel. Not for everyone but works for some.
Thank you annlonie - glad you read it and found it interesting.
We coach by feel - and even those who like numbers do eventually learn that this is a better way to train, and race.
Our body is designed to know itself when we allow it to and forget numbers