Lord Ram had returned to Ayodhya, and after the coronation ceremony, Ram and Sita sat on the throne as King and Queen. Just then, Lakshman yawned, then smiled, and the smile turned into laughter.
Ram thinks that Lakshman is laughing at him, for having waged a war, with accompanying misery, pain and death for many soldiers and their families. Lakshman is laughing that the coronation was based on much sadness.
Sita thinks of all the wars waged over her, and her carelessness in letting Ravana kidnap her. Her becoming Queen and sitting with Ram on the throne is therefore not a cause to celebrate, and Lakshman is laughing at her.
Kaikeyi was responsible for sending Ram to the forest, since she wanted her own son to be king. Since her scheming calculations did not work, and Ram was anointed king, Kaikeyi thought that Lakshman was making fun of her, by laughing at her failures.
The people of Ayodhya thought that even as Ram had departed for the forest, they had continued to live in the city. Lakshman was now taunting them, and laughing at their timid nature. Only Vishwamitra asks Lakshman to explain his laughter.
Lakshman says that fourteen years ago, he had prayed to the goddess of sleep to never come near him, till Ram returns as king. Just as Lord Ram sat on the throne, he yawned and felt sleepy, with goddess of sleep returning as she had promised.
Guru Granth Sahib says: This mind is a mirror;// Rare are those who examine what they see.
Just like Lakshman’s laughter had a different meaning for everybody, our perception of the world is based on our thinking. Our negative thoughts should caution us about the negativity inside of us. As we cleanse ourselves of anger, greed, and jealousy, we fill with positivity and love for all.