Colgando is the Spanish gerund for "hanging". While it can be used literally, this song uses it in a beautiful and romantic metaphor that forms the core of the entire track.
Carlos Baute sings, "Sabes que estoy colgando en tus manos, así que no me dejes caer" (You know that I'm hanging in your hands, so don't let me fall). This phrase paints a vivid picture of vulnerability and complete trust, as if his fate and his heart are literally suspended in his lover's hands.
This song is a huge, romantic declaration of love! Carlos Baute and Marta Sánchez sing about a love that feels like it was meant to be, starting with the line "Quizá no fue coincidencia encontrarme contigo / Tal vez esto lo hizo el destino" (Maybe it wasn't a coincidence meeting you / Maybe destiny did this). The whole song is built around the idea of being completely vulnerable with someone. The main line, "Sabes que estoy colgando en tus manos / Así que no me dejes caer" (You know I'm hanging in your hands / So don't let me drop), is such a dramatic way to say "I'm putting all my trust in you."
To make sure his love is remembered, the singer sends all sorts of romantic things: handwritten poems, songs, and photos from their trips to Marbella and Venezuela. It's a sweet, slightly over-the-top gesture. But there's also a warning that comes with this total vulnerability: "Cuidado, cuidado / Que mi corazón está colgando en tus manos" (Be careful, be careful / Because my heart is hanging in your hands). It's a passionate plea for the other person to handle their heart with care.