Analysis:
This quatrain by Saadi Shirazi offers a sobering perspective on life, love, and the fickleness of fortune.

The Futility of Hope: The first couplet suggests that placing too much hope in the passage of time or in external circumstances is futile. It implies that dwelling on past sorrows only leads to more suffering.
Betrayal by Friends: The second couplet highlights the pain of betrayal, especially when it comes from a friend. It questions what recourse one has when even those closest to us cause us harm.
The Inescapable Nature of Suffering: The overall theme is the inevitability of suffering and the limitations of human agency in the face of adversity.

Themes:

The Passage of Time: The quatrain reflects on the passage of time and how it can exacerbate our sorrows if we dwell on the past.
Betrayal and Trust: The theme of betrayal, especially by friends, is central to the quatrain.
The Limitations of Human Agency: The speaker suggests that there are certain aspects of life that are beyond our control.

Deeper Meaning:

This quatrain offers a philosophical reflection on the human condition. It suggests that while hope is essential, excessive reliance on it can lead to disappointment. Moreover, the pain of betrayal can be particularly profound, especially when it comes from those we trust. The final couplet implies a sense of resignation, suggesting that there are certain aspects of life that we must simply accept.

This quatrain is a reminder of the impermanence of life and the importance of finding inner peace amidst external suffering.