With this shloka, Krishna begins painting the portrait of His dearest devotee. The first brushstroke: no hatred toward any living being. Not partial kindness — universal. Friendly to all. Compassionate to all. This is not selective warmth offered only to people who are pleasant or convenient.
Then two inner freedoms: no possessiveness ('mine-mine') and no ego ('I-I'). These two chains bind human beings more tightly than anything else. The person who loosens them becomes light — the way a cloud becomes light after releasing its rain.
Equal in joy and sorrow, and forgiving. When someone wrongs you, you let it go. When pain arrives, you do not crumble. The way grandparents forgive their grandchildren's mistakes almost before the mistakes are finished — that natural grace is what Krishna describes in the devotee closest to His heart.