I wonder if the old man is warning others to follow their dreams and achieve their goals while they can. He must realize it is too late and he can "dream no more dreams." Maybe there is something he didn't accomplish, but he wishes for others to achieve their dreams. "May it be a warning to all the children and people in every land" makes me think that the old man is trying to influence the youth so they don't make the same mistakes he has. He has more experience as he has lived a long life.
Explanation:
This is what I inferred from the poem, idk if it is right or not.
