Desmorono comes from the verb desmoronarse, meaning 'to crumble' or 'to fall apart'. It's a vivid and dramatic word that goes beyond simply saying 'I feel bad'.
In the song, the artist sings, "Cuando no nos vemos, yo me desmorono" (When we don't see each other, I crumble). This powerfully conveys the depth of his emotional dependence and how completely lost he feels without his loved one, making it a very impactful choice.
In "Cuatro Días," which translates to "Four Days," Alvaro De Luna sings about a love that feels like a high-stakes game against time. He declares he has just four days to win someone's heart, but he's not worried. Why? Because he sees them as the "best team" that can win any "fucking game." For him, love is a battle, but he's not afraid of losing because simply being with this person already feels like a victory.
The singer reveals just how deeply this person affects him. He feels empty without their warmth, even in a crowded city, and realizes that the party lifestyle means nothing compared to being with them. He makes a powerful statement: this isn't dependency, but a feeling of being his truest self only when they are together. It's an all-or-nothing commitment, as he sings, "If we go, we go with everything."