That by which one sees the one indestructible Reality in all beings, not separate even in all the separate beings - know thou that knowledge to be Sattvika (pure).
But that knowledge which sees in all beings various entities of distinct kinds as different from one another - know thou that knowledge to be Rajasika.
But that which clings to one single effect as if it were the whole, without reason, without foundation in Truth, and trivial- that (understanding) is declared to be Tamasika. (XVIII20-22)
Three Kinds of Happiness
That which is like poison at first but in the end like nectar - that happiness is declared to be Sattivaka, born of the purity of one's own mind due to Self-realisation.
That happiness which arises from the contact of the sense-organs with the objects, which is at first like nectar, and in the end like poison - that is declared to be Rajasika.
That happiness which at first as well as in the sequel deludes the self, and which arises from sleep, indolence and heedlessness - that is declared to be Tamasika. (XVIII.37-39)
Perfection Is Attained by Performance of One's Own Duty Without Interfering with Another's
He from whom all the beings have evolved and by whom all this is pervaded - worshipping Him with one's own duty, one attains perfection. (XVIII.46)
Resort to God Is the Solution of All the Ills of Life
Abandoning all duties, take refuge in Me alone; I will liberate thee from all sins; grieve not. (XVIII.66)
Success Is Certain Where Man and God Act in Unison
Where is Krishna, the Lord of Yoga; where is Arjuna, the wielder of the bow, (acting together in harmony); there shall be prosperity, victory, happiness and firm polity; this is my conviction. (XVIII.78)