They should lift the world forward. That is what they are for. Live Welcoming to all. Optimism includes not only altruism but also social responsibility, social courage and objectivity. Those who are not looking for happiness are the most likely to find it, because those who are searching forget that the surest way to be happy is to seek happiness for others.
Life begets life.
Energy creates energy. It is by spending oneself that one becomes rich. This is the true joy in life, the being used for a purpose recognized by yourself as a mighty one, the being thoroughly worn out before you are thrown on the scrap heap, the being a force of nature instead of a feverish little clod of ailments and grievances complaining that the world will not devote itself to making you happy. The ready back gets all the loads. No one can sincerely try to help another without helping himself.