Here is the Jain concept of equanimity (samāyikā/sāmāyika) in brief, with a simple verse-like line that is commonly taught in Jain tradition. In Jainism, equanimity is the practice of viewing all living beings with equal regard, keeping the mind steady, and restraining anger, attachment, and aversion.

Original essence (arth) in Jain terms:

• Equanimity is one of the six obligatory actions (avashyaks) for both monks and householders; it guides mind, speech, and action toward equal regard for all beings.
• It is cultivated through threefold restraint (body, speech, mind) and through non-attachment, so that one remains steady in happiness and sorrow alike.

Simple, traditional guiding line (conceptual rendering):

• May the mind remain equal toward all beings, in joy and suffering, praise and blame, honor and insult.

Notes:

• There are nuanced differences in how Digambara and Śvetāmbara traditions articulate and meter such verses, but the central aim—samāyika or samatā (equanimity) as a core practice—remains the same.

If you’d like a precise, traditional verse text and its exact meaning as per a specific Jain sect (Digambara or Śvetāmbara), I can provide that. You can also read more about samāyika and equanimity in Jain tradition on the JainKnowledge site.