Boxes in the head tend to contain things that you don't want to remember. They sit in the corner collecting cobwebs of fear and paranoia as you do your best never to go near them. But sometimes a memory, a piece of music, a tone of voice even can cause them to explode open and their destructive contents flow out tainting everything they touch. You have to fight to get them back where they belong. It is like sitting on a bulging box trying to seal it up again before anything else escapes.
Whilst boxes in the heart tend to be cared for. They are polished with love and the knowledge no one will ever know what's in them. They are stacked neatly and protectively. Their contents are not nasty they are emotions and desires that can never be acknowledged openly. They are things that other people don't need to know often because it will cause someone else pain. Boxes in the heart don't like to hurt people.
I think boxes make writers and writers make boxes. Life would be very quiet without them as they are never silent, they do like you to know they are there. Waiting, biding their time, just in case they are allowed to fly free as a bird.
I like boxes. particularly the ones in the heart with their golden moments. But rest assured no one will every know what my boxes contain. Ssshh, they're a secret ;-)