al-Ghazzali said

Man is envious like an ox, greedy like a pig, bites like a dog, eats like a camel, takes revenge like a leopard, is cunning like a fox and clever like a devil

The discipline of tazkiya subordinates man’s animal instincts to his higher human inclinations

Man vacillates between the two poles of good and evil, and tazkiya is his path toward good, and therefore also towards God

Only through the refinement of the souls and characters of individuals  can a healthy society be created. Individuals are like the bricks from which the edifice of society is built unless the bricks are strong, mere alteration in the design and structure will not produce any lasting results. The attainment of justice and the other aims of social life can be achived only by moral and spiritual means, which are the building-blocks of the political and economic structure of society

A manual of Islamic Beliefs and Practice/A.Naqavi/p:24