Virtue is not just following the precepts, but it’s a quality of mind that’s solid in its intentions. You make up your mind that you’re going to avoid evil, and then you just stick with that intention. That’s the essence of virtue.

"Virtue is not just following the precepts, but it’s a quality of mind that’s solid in its intentions. You make up your mind that you’re going to avoid evil, and then you just stick with that intention. That’s the essence of virtue. The word “sila” in Pali is related to the word “sela,” which means rock. In other words, there’s a solidity to that intention that you hold onto. You don’t let it go.

Initially it may not seem like much, but you find that as you really hold onto these intentions — “Not to harm, not to harm, not to harm” — it really protects the mind from a lot of things. You learn not only not to harm people outside, but you also learn how not to harm yourself. And as you don’t harm yourself, you find resources of strength in your mind that you wouldn’t have guessed at otherwise. Because as long as the mind is harming itself, it keeps sapping its own strength, thinking in ways that get it depressed, thinking in ways that get it fearful, that just drain its strength away. So when you learn to give up those habits, you find resources of strength inside that you wouldn’t have anticipated. You can hold onto them."

~ Thanissaro Bhikkhu "The Line of Fire"