What should a Baha’i center his/her thoughts on and yearn for?

Consequently, one must close his eyes wholly to these thoughts, [“material rest, tranquillity, luxury and attachment to this corporeal world”] long for eternal life, the sublimity of the world of humanity, the celestial developments, the Holy Spirit, the promotion of the Word of God, the guidance of the inhabitants of the globe, the promulgation of universal peace and the proclamation of the oneness of the world of humanity! This is the work! Otherwise like unto other animals and birds one must occupy himself with the requirements of this physical life, the satisfaction of which is the highest aspiration of the animal kingdom, and one must stalk across the earth like unto the quadrupeds. (‘Abdu’l-Baha, ‘Tablets of the Divine Plan’)