Life is not a pleasure, but a very heavy work. ——Leo Tolstoy The value of life is not measured by time, but by depth. ——Leo Tolstoy · For a person who is immersed in mental work, if he does not move his limbs regularly, it will be an extremely painful thing. · Heroism consists in sacrificing oneself for faith and truth. · The career of science is to serve the people. · Life is not a pleasure, but a very heavy task. ·Ideal books are the key to wisdom. · A mind without wisdom is like a lantern without candles. · People are too accustomed to using force to maintain order that it is impossible to think about social organization without repression. ·