One should not rejoice having attained the pleasant, nor should one shudder having attained the unpleasant. With steady understanding (buddhi), unbewildered, the knower of Brahman is established in Brahman.
He should not rejoice in what he loves nor recoil from what disgusts him; secure in understanding, undeluded, knowing the infinite spirit, he abides in it.
(20) Winning some pleasant thing [the sage] will not rejoice, nor shrink disquieted when the unpleasant comes his way: steadfast-and-still his soul, [all] unconfused, he will know Brahman, in Brahman [stilled] he'll stand.
5.20 A knower of Brahman, who is established in Brahman, should have his intellect steady and should not be deluded. He should not get delighted by getting what is desirable, nor become dejected by getting what is undesirable.
5.20 He who knows Brahman (individual self) and abides in Brahman, whose mind is steadfastly on the self and undeluded by the body consciousness --- he neither rejoices at gaining what is pleasant, nor grieves on obtaining what is unpleasant.
5.20 Resting in Brahman, with steady intellect and undeluded, the knower of Brahman neither rejoiceth on obtaining what is pleasant nor grieveth on obtaining what is unpleasant.