Ivresses is the plural of ivresse, which literally means "drunkenness" or "intoxication." However, it can also refer to a state of intense excitement, ecstasy, or elation.
In the context of the song, the artist sings "Pour ces ivresses de quelques heures" (For these ecstasies of a few hours). This suggests a willingness to trade wisdom for fleeting moments of intense joy or passion, even if they lead to mistakes. It's a more poetic and less common word than simply saying "joie" (joy), making it intriguing.
"Tomber" ("To Fall") is Ycare's declaration that he's ready to fall in love again, fully aware of the risk.
He admits he might repeat the same gestures, the same painful breakups, and even the same mistakes as before. He's willing to trade his hard-won wisdom for a few hours of intoxicating passion, because the second half of life is too short not to love with his whole heart.
The repeated "Tomber" hook ("to fall", "if I have to fall", "I want to fall in love") captures that surrender: he knows falling in love means losing his balance and risking heartbreak again, but he takes the risk anyway, believing happiness is worth chasing even when chance plays no part in it.