Arenas movedizas literally translates to 'quicksand' in English. It is formed by combining arenas (sands) with movedizas (shifting or moving), creating a highly visual phrase for an unstable trap that pulls you under.
In this emotionally charged song, Shakira uses the phrase as a powerful metaphor to describe her profound sense of isolation. She sings about sinking into her loneliness like quicksand, beautifully capturing the physical sensation of being trapped and overwhelmed by sadness when missing the person she loves.
Shakira gets incredibly real in this song about feeling completely lost and overwhelmed. She describes a life where even music has lost its magic and every day feels the same, asking, "Ya no sé si he vivido diez mil días o un día diez mil veces" (I don't know if I've lived ten thousand days or one day ten thousand times). It's a powerful way to talk about feeling stuck in a loop of sadness. She uses some intense images to describe her state of mind, feeling lost "como una aguja en un pajar" (like a needle in a haystack) and sinking into her own loneliness like it's quicksand.
Amidst all this confusion and despair, the chorus is a direct and desperate plea to someone she loves. She's not just missing them; she feels she literally can't function without them. She admits, "Y es que no sé vivir sin ti / No he aprendido" (It's just that I don't know how to live without you / I haven't learned). This person is her only hope for changing her "pérdidas por creces" (losses into gains) and bringing warmth back into her life. It's a song about needing someone so much that they feel like a part of you.