Confucius:

To put the world right in order, we must first put the nation in order; to put the nation in order, we must first put the family in order; to put the family in order, we must first cultivate our personal life; we must first set our hearts right.

Ecclesiastes:

For everything there is a season,
And a time for every matter under heaven:
A time to be born, and a time to die;
A time to plant, and a time to pluck up what is planted;
A time to kill, and a time to heal;
A time to break down, and a time to build up;
A time to weep, and a time to laugh;
A time to mourn, and a time to dance;
A time to throw away stones, and a time to gather stones together;
A time to embrace, And a time to refrain from embracing;
A time to seek, and a time to lose;
A time to keep, and a time to throw away;
A time to tear, and a time to sew;
A time to keep silence, and a time to speak;
A time to love, and a time to hate,
A time for war, and a time for peace.

Ecclesiastes 3:1-8

H.H. the Dalai Lama:

The basic thing is that everyone wants happiness, no one wants suffering. And happiness mainly comes from our own attitude, rather than from external factors. If your own mental attitude is correct, even if you remain in a hostile atmosphere, you feel happy.

Helen Keller:

When one door of happiness closes, another opens; but often we look so long at the closed door that we do not see the one which has been opened for us.