Fiato means "breath" in Italian. While it might seem like a common word, its repeated use in the phrase "senza fiato" (breathless) is central to the song's theme and title.
The song is titled "Senza Fiato," and the lyrics repeatedly express a desire to live life so intensely that it leaves one "senza fiato"—literally without breath, but metaphorically overwhelmed, exhilarated, and fully alive. This makes fiato a powerful and evocative word in the context of the song.
Have you ever felt like you're overthinking everything? That's the feeling Michele Bravi is kicking to the curb in this song. He's completely done with weighing "Tutti i pro e i contro delle mie azioni" (All the pros and cons of my actions) and trying to act with moderation. He's tired of changing for other people and making compromises, declaring, "Non vengo più a patti con niente con nessuno" (I'm not making deals with anything or anyone anymore).
Instead, he makes a powerful decision: to live life to the absolute fullest. The main idea is right there in the chorus: "Io voglio solo vivere ogni secondo / Come fosse l'ultimo" (I just want to live every second / As if it were the last). He doesn't care if his choices are right or wrong; he just wants to experience everything so intensely that it leaves him "senza fiato" (breathless). It's all about letting go of the past, shedding inhibitions, and living a life with no regrets.