As difference in degree of capacity exists among human souls, as difference in capability is found, therefore, individualities will differ one from another.  But in reality this is a reason for unity and not for discord and enmity.  If the flowers of a garden were all of one color, the effect would be monotonous to the eye; but if the colors are variegated, it is most pleasing and wonderful.  The difference in adornment of color and capacity of reflection among the flowers gives the garden its beauty and charm.  Therefore, although we are of different individualities, different in ideas and of various fragrances, let us strive like flowers of the same divine garden to live together in harmony.  Even though each soul has its own individual perfume and color, all are reflecting the same light, all contributing fragrance to the same breeze which blows through the garden, all continuing to grow in complete harmony and accord.  Become as waves of one sea, trees of one forest, growing in the utmost love, agreement and unity.

"The Promulgation of Universal Peace," p. 24

It is extremely difficult to teach the individual and refine his character once puberty is passed. By then, as experience hath shown, even if every effort be exerted to modify some tendency of his, it all availeth nothing. He may, perhaps, improve somewhat today; but let a few days pass and he forgetteth, and turneth backward to his habitual condition and accustomed ways... 

"Selections from the Writings of Abdu'l-Baha," p. 137

Every man trained through the teachings of God and illumined by the light of His guidance, who becomes a believer in God and His signs and is enkindled with the fire of the love of God, sacrifices the imperfections of nature for the sake of divine perfections.  Consequently, every perfect person, every illumined, heavenly individual stands in the station of sacrifice.

“The Promulgation of Universal Peace,” p. 452

Attach not thyself to anything unless in it thou seest the reality of God - this is the first step into the court of eternity.  The earth life lasts but a short time, even its benefits are transitory; that which is temporary does not deserve our heart's attachment.

“Divine Philosophy,” p. 134

What becomes of the soul after its separation from the body?

... The question concerns that which has a place and that which is placeless.  The human body is in space; the soul has no place in space.  Space is a quality of material things and that which is not material does not partake of space.  The soul, like the intellect, is an abstraction. Intelligence does not partake of the quality of space, though it is related to man's brain.  The intellect resides there, but not materially.  Search in the brain you will not find the intellect.  In the same way though the soul is a resident of the body it is not to be found in the body.

"Divine Philosophy," p. 12