In the Bhagavad Gita, Sri Krishna speaks of three qualities or gunas: tamas, rajas and sattwa. All mental states and expressions of life are governed by tamas, rajas and sattwa. There is no thought and no action which is free from the influence of these gunas. Therefore, you have to know the gunas before you understand any other concept of yoga.
There is no use defining kama, krodha, lobha, moha, mada, and matsarya, desire, anger, greed, infatuation, pride and envy, unless they are seen in relation to the gunas.
An example is the knife, is it good or bad? The goodness or badness of the knife is determined by its use. The knife itself does not have a quality.
One can see that the quality of the knife is to cut. That is an action of the knife, yet the action is guided and controlled by the three gunas. If the tamasic guna pushes the knife into somebody’s heart and kills that person, it is the tamasic act in which the knife became an instrument to fulfil it. The knife is not tamasic. It became a medium to fulfil a tamasic act.
Similarly, if you use the knife to chop vegetables, prepare your meal to sustain yourself, the knife is being used in a rajasic manner. The same knife in order to save the life of somebody is being used in a sattwic manner. Knife is a word, but its actions are guided by the gunas.
Krodha, anger, becomes positive when associated with sattwa guna. Krodha becomes negative when associated with tamoguna. Krodha becomes corrective when associated with rajoguna. The six enemies kama, krodha, lobha, moha, mada and matsarya are only words, nothing more than that. They become something when in association with a particular guna.
—18 October 2015, Ganga Darshan, Munger