Analysis:

This quatrain by Saadi Shirazi expresses deep pain and betrayal experienced in a relationship. The speaker is lamenting the fickle nature of their beloved and taking responsibility for the pain inflicted.

Line 1: آن سست وفا که یار دل‌سخت من است

"That fickle lover, my stone-hearted beloved,"
Here, the beloved is described as being unfaithful and having a stone-like heart. The word "سست وفا" (sost-vafa) emphasizes their lack of loyalty.

Line 2: شمع دگران و آتشِ رخت من است

"Is a candle to others, but a fire to my clothes."
This line creates a striking contrast. The beloved is like a candle that provides light and warmth to others, but for the speaker, they are like a fire that is consuming them.

Line 3: ای با همه کس به صلح و با ما به خلاف

"O you who are at peace with all but me,"
The speaker addresses the beloved, noting their peace with everyone else except themselves. This highlights the exclusivity of the pain they are experiencing.

Line 4: جرم از تو نباشد گنه از بخت من است

"The fault is not yours, but my ill-fortune."
The speaker takes responsibility for their suffering, attributing it to their bad luck rather than blaming the beloved. This shows a remarkable level of self-awareness and compassion.

Themes explored in the quatrain:

Unrequited love: The speaker's love is clearly unrequited, leading to immense pain.
Betrayal and heartbreak: The beloved's fickleness has caused deep emotional pain.
Self-blame: The speaker takes responsibility for their suffering, showing a mature understanding of their situation.

This quatrain is a poignant expression of heartbreak and the complexities of love. It captures the universal experience of feeling betrayed by someone you care about. The speaker's acceptance of their fate, even in the face of such pain, is a testament to their strength and resilience.