Krishna says, "Those devotees are very dear to Me who do not hate any being, who are friendly and compassionate, who are 𝙣𝙞𝙧-𝙢𝙖𝙢𝙖 (𝙨𝙖𝙣𝙨-𝙄) 𝙖𝙣𝙙 𝙣𝙞𝙧-𝙖𝙝𝙖𝙣𝙠𝙖𝙖𝙧 (𝙨𝙖𝙣𝙨 -𝙄 𝙖𝙢 𝙙𝙤𝙚𝙧), who are balanced in pleasure and pain (𝙨𝙖𝙢𝙖-𝙙𝙪𝙠𝙝-𝙨𝙪𝙠𝙝) and forgiving (𝙠𝙨𝙝𝙖𝙢𝙞) . Who are ever-content, self controlled yogi, having firm conviction, and who have their mind and intellect dedicated to Me" (12.13 and 12.14).
At the outset, this appears to run contrary to Krishna's earlier assurance that none is 𝙙𝙬𝙚𝙨𝙝𝙮𝙖 (hateful) and none is 𝙥𝙧𝙞𝙮𝙖 (dear) to Him (9.29). While HIS blessings are available to everyone like rain, possessing these qualities is like keeping our bowl upright.
'Not hating anyone' is at the core of the Bhagavad Gita. Earlier Krishna advised to perform 𝙠𝙖𝙧𝙢𝙖𝙨 (actions) by dropping hatred (5.3). When hatred becomes a part of us, shedding it becomes painful as it makes us lose a part of ourselves. It's like removing a harmful cancerous tumor, removal of which will still cause pain to us.
On the other hand, it is essential to drop hatred as it drives our behaviour and actions. 'Forgiveness' is the best antidote for hatred. Forgiveness requires courage and inculcating 𝙨𝙖𝙢𝙖𝙩𝙫𝙖 (equanimity) gives that courage. 𝙎𝙖𝙢𝙖𝙩𝙫𝙖 is not only treating things and people as equal but also realising that we too possess the same negative qualities like greed and anger suppressed within us. Conversely, we have an aversion to these traits when we find them in others.
Krishna earlier said that 𝙣𝙞𝙧-𝙢𝙖𝙢𝙖 𝙖𝙣𝙙 𝙣𝙞𝙧-𝙖𝙝𝙖𝙣𝙠𝙖𝙖𝙧 is the path for peace (2.71). Similarly, 'ever content' is another foundational principle in the Gita. Essentially, when one quality is attained, others will follow automatically as they are interconnected. It's about identifying one of these traits that suits us and mastering it at the existential level.