Bhagavad Gita 5.18-20

 "Those whose minds are established in sameness and equanimity have already conquered the conditions of birth and death. They are flawless like Brahman, and thus they are already situated in Brahman. A person who neither rejoices upon achieving something pleasant nor laments upon obtaining something unpleasant, who is self-intelligent, who is unbewildered, and who knows the science of God is already situated in transcendence."