The speaker can understand that his dead friend is already depressed and hopeless. The things he has imagined have not come true. Everything is normal and adapted to the change. Likewise, his sweetheart is also content with her new life. So, not to depress his friend any further, he does not say with whom he is with directly. However, he hints at the fact he is with his friend's beloved by the lines "I cheer a dead man's sweetheart,/ Never ask me whose."