I do not like that particular quote. I can offer you mine: "when you are not resting, someone else is. when you meet him, he will win."

Bruce Lee changed his "be as ready to fight as possible every day" attitude which didn't allowed him to be the best - he had to train less intensely than possible. So he introduced two one day rests and one two days rest into his training regimen.

Sayings like that (quoted by article author and one from your trainer) are manipulative and provoke sense of guilt without any good reason.