What did Antoine mean when he said the burden in a lesson before dying?

Antoine meant that the burden in the lesson "Before Dying" was the weight of the guilt he felt for committing a murder for which he was wrongfully convicted. He saw his wrongful conviction as a test of his character, and he sought to prove his innocence and reclaim his freedom. The burden weighed heavily on him, affecting his physical and emotional well-being. Antoine's determination to overcome this burden and fight for justice drives the narrative of the story.