Arrancado de raíz literally translates to "torn out by the root" or "uprooted." It's a vivid and somewhat dramatic phrase that you don't encounter in everyday conversation, making it memorable.
In the song, Beret uses this phrase to describe a profound personal transformation, singing, "Me he arrancado de raíz, ¿acaso no veis que estoy volviendo a crecer?" (I've uprooted myself, don't you see that I'm growing again?). It powerfully conveys the idea of completely detaching from his past to start anew and grow.
Beret's "Hoy" is all about embracing the present and finding happiness right now. He's basically saying, "What am I going to do if I'm happy, lady?" [Y qué le voy a hacer si soy feliz lady]. It's a song about moving on from past hurts and choosing to grow. He talks about how he's "torn himself out by the roots" [Me he arrancado de raíz] and is now "growing again" [Estoy volviendo a crecer] because everything is going well.
He acknowledges that it's been tough to appreciate the good moments and that scars have made him late to things, but he's firm that "better late than never to stay" [mejor tarde que nunca para quedarme]. Beret is done being angry and says, "I had time to get angry, but not today" [Ya tuve tiempo para enfadarme pero no hoy]. He's letting go of the past, closing doors, and focusing on being himself, at least for today. It's a really uplifting message about self-acceptance and living in the moment.