The Bhagavad-Gita calls on humanity to dedicate body, mind and soul to pure duty and not to become mental voluptuaries at the mercy of random desires and undisciplined impulses.
These two rational faculties may be designated the Scientific Faculty and the Calculative Faculty respectively; since calculation is the same as deliberation, and deliberation is never exercised about things that are invariable, so that the Calculative Faculty is a separate part of the rational half of the soul.
There is nothing more harmful to you than improving only your material, animal side of life. There is nothing more beneficial, both for you and for others, than activity directed to the improvement of your soul.
The soul comes from without into the human body, as into a temporary abode, and it goes out of it anew it passes into other habitations, for the soul is immortal.
As a rule, the mind, residing in a body that has become weakened by pampering, is also weak, and where there is no strength of mind there can be no strength of soul.
He that can heroically endure adversity will bear prosperity with equal greatest of the soul; for the mind that cannot be dejected by the former is not likely to be transported without the latter.
Opinion involves belief (for without belief in what we opine we cannot have an opinion), and in the brutes though we often find imagination we never find belief.