Magoar means 'to hurt' or 'to wound' someone emotionally. It's a strong verb that goes beyond just 'to make sad' and implies a deeper, more significant emotional injury.
In the context of "Por Te Amar Demais," the singer uses magoar when warning about the pain of love: "Se apaixonar e alguém magoar você" (If you fall in love and someone hurts you). It highlights the vulnerability and potential for deep emotional pain in relationships, making it a poignant and memorable word in this romantic ballad.
"Por Te Amar Demais" is Gusttavo Lima singing to someone who left without warning, after he had given everything to the relationship. He tells her plainly that she'll come to regret it: she didn't value what he felt, and one day she'll remember how much he loved her.
The chorus turns the song's title into its warning. If she ever falls for someone else and gets hurt in return, she'll think back to this love and see what she gave up. By the bridge he softens, saying he forgives her and forgets what she did, because loving someone this much is simply who he is.
It's a classic sertanejo heartbreak song: hurt pride mixed with real tenderness, ending on forgiveness rather than bitterness.