We pack, I think, in much the same way that we live - anticipating possible eventualities, and feeling that if we are only well prepared, we will be able to deal with whatever we encounter in a way that will not cause us too much discomfort. We project our anxiety about the future onto things - if I have my wool socks my feet will never be cold, if I have enough books I'll never be bored, and so on. Our things become fetishes, magical objects that can ward off the malignant spirits that seek to do us harm and cause us to suffer.
But there is a wisdom to be found in not overpacking for a trip. By traveling light, we show an acceptance of the reality that we are destined to suffer. Despite all our preparations, our planning and packing, we inevitably will find ourselves in difficult and unpleasant situations. We cannot reasonably hope to guard ourselves from all that might befall us. When we realize this, we may come to see our things as burdens rather than guardians, weights that drag on us and limit our mobility. Walled in by mountains of stuff, we are cut off from the thrilling challenges of life.
Having made the incredibly daring decision to go to Bolivia, push it one step further and truly open yourself to the possibilities.