Here is a speaker admitting to something quietly painful: telling themselves lies, not to deceive anyone else, but to protect their own heart. The poem is only three short lines, and its brevity fits the subject. There is no long explanation, just a confession.
The opening "And," feels like the middle of a thought, as if the speaker has been turning this over for a while and finally lets it slip out. The word "whispered" matters too. Whispering suggests secrecy and softness, the way you might soothe a frightened child. Here the speaker is both the comforter and the one being comforted.
The final line gives the reason: "Just to avoid more damage." The word "more" tells us the heart has already been hurt. The lies aren't meant to make things better, only to stop them getting worse. The mood is tender but weary, a little sad, and quietly honest about how people sometimes cope by not looking too closely at the truth.