Shaykh Abu Yazid (may Allah have mercy on him) was asked,

‘When does an individual acquire true humility?’

He replied, “When being aware of the mischief and bad traits of it he realizes that his lower-self (nafs) does not have any rights at all. And he does not consider anyone else inferior to himself.”

 Awarif al-Ma’arif, page 296

An essential reading for all salikeen from the curriculum of Tasawwuf.