Be unselfish. That is the first and final commandment for those who would be useful, and happy in their usefulness. If you think of yourself only, you cannot develop because you are choking the source of development, which is spiritual expansion through thought for others.
Don't think too much about yourselves. Try to cultivate the habit of thinking of others; this will reward you. Nourish your minds by good reading, constant reading. Discover what your lifework is, work in which you can do most good, in which you can be happiest. Be unafraid in all things when you know you are in the right.
Whatever deprives a man of personal individual motive for self-improvement and robust exertion will not make him free, but on the contrary more servile and in the long run less intelligent, industrious and free, for freedom is a matter of character and will power.