Regarding the question you asked in your letter: The only people who are truly free of the "dross of self" are the Prophets, for to be free of one's ego is a hallmark of perfection. We humans are never going to become perfect, for perfection belongs to a realm we are not destined to enter. However, we must constantly mount higher, seek to be more perfect.
The ego is the animal in us, the heritage of the flesh which is full of selfish desires. By obeying the laws of God, seeking to live the life laid down in our teachings, and prayer and struggle, we can subdue our egos. We call people "saints" who have achieved the highest degree of mastery over their ego.
There is no contradiction between Gleanings" p. 66 and p. 262. In one place He says the mirror will never be free from dross, in the other He says it will be "so cleansed . . . as to be able," etc. It is relative thing; perfection will never be reached, but great, and ever greater, progress can be make.
- Shoghi Effendi (From a letter dated 8 January 1949 written on behalf of Shoghi Effendi to an individual believer; compilation: ‘Psychology and Knowledge of Self’, prepared by the Research Department of the Universal House of Justice, attached to a letter dated 23 October 1994 written on behalf of the Universal House of Justice to an individual believer; Baha’i Library Online)