We must have a pure, honest, and warm-hearted motivation, and on top of that, determination, optimism, hope, and the ability not to be discouraged. The whole of humanity depends on this motivation.
Material objects give rise to physical happiness, while spiritual development gives rise to mental happiness. Since we experience both physical and mental happiness, we need both material and spiritual development. This is why, for our own good and that of society we need to balance material progress with inner development.