The box knows all, yet the box does not tell.
An analysis of the painting shows that the words were added later, and were not contemporaneous with the image. This suggests they were appended to the work by anti-boxers, who believed - with almost frightening zeal - that the box sapped the individual's will and ability to reason or discriminate.
It is, perhaps, ironic: so many of the works that venerate the box and show its ability to produce happiness and pleasure were easily turned against the box, showing how it took away a man's strength.
The words, in short, may constitute a threat to the pro-box forces. Change your ways or you will be beaten.