Lamenting in times of sorrow and rejoicing in times of joy are the marks of a friend, Contrary actions from the indications of an enemy.
आर्तिराते प्रिये प्रीतिरेतावन्मित्रलक्षणम्। विपरीतं तु बोद्धव्यमरिलक्षणमेव तत्॥