Dr. Matthew Hinsley coined the mantra "Small Parts, More Times, Better." As a constant reminder of this idea, write the acronym SPMTB on the top of every piece you intend to learn.
To apply this concept to Carcassi's Andante, choose a small section (one or two measures at the most) that you find to be challenging. Set a goal of 10 perfect repetitions at a slow pace. After you master any problem areas, put them back into the context of the whole piece.