Why does juan censor his own letter to mariana “ without regret “

It might be said that Juan censors his letter to Mariana in order to protect themselves. He need to censor it in order to be safe. It was a difficult time in Argentina where any negative or suspicious comment about the government or a related topic would let you to you death. but he ends up so obsessed with censorship that he is not able to recognize his own letter.

What does that mean