Tirmidhi

Explanation of the Hadith:

What I know, if you were to know as well:

There are several statements regarding this, the general meaning of which is that "the intent of the Prophet’s (sallallahu alayhi wa sallam) statement is matters of the Hereafter, its hardships, the terrors of Hell, the punishment of sinners, and the conditions of death and the grave, etc. The reality of these is known only to me; if you were to know it, you would laugh very little." (Fath al-Bari: 11/527-528)

From these words, it is also understood that in the heart of the Prophet (sallallahu alayhi wa sallam), the fear and awe of Allah was extremely great, to a degree that could never be in anyone else’s heart. Furthermore, the Messenger of Allah (sallallahu alayhi wa sallam) said: ((إِنِّي أَخْشَاكُمْ لِلَّهِ وَأَتْقَاكُمْ لَهُ)) "I am the one among you who fears Allah the most and is the most mindful of Him." (Fath al-Bari: 11/527-528)

This hadith also demonstrates the virtue of the Prophet (sallallahu alayhi wa sallam).

You would weep more and laugh less:

The Prophet (sallallahu alayhi wa sallam) said this to the Companions to instill fear in them, so that they would not fall into heedlessness, even temporarily, and so that the fear of Allah would always remain in their hearts.

Hasan al-Basri (rahimahullah) said: "Whoever knows that death is certain to come, that the Day of Judgment will be established, and that he will have to stand before Allah and give account, it is necessary for him to spend a long portion of his life in this world in sorrow and grief." (Fath al-Bari: 11/319-320)

The Messenger of Allah (sallallahu alayhi wa sallam) is the greatest interpreter of the Noble Qur’an. This hadith of his is an explanation of Allah the Exalted’s statement:

فَلْيَضْحَكُوا قَلِيلًا وَلْيَبْكُوا كَثِيرًا جَزَاءً بِمَا كَانُوا يَكْسِبُونَ (al-Tawbah: 82)
"So let them laugh a little and weep much, as a recompense for what they used to earn."

Ibn Abu Talhah narrated from Ibn Abbas (radi Allahu anhuma) that the life of this world is very brief; let them laugh as much as they wish in it, but when the world ends and they reach Allah the Exalted, they will have to weep so much that it will never end. (Tafsir Ibn Kathir: 3/135, Darussalam edition. Tafsir Ibn Abi Hatim: 6/1855)

As the poet says:
Do not let constant laughter destroy you,
In moments of solitude, sometimes weep as well.