子曰：“学而时习之，不亦悦乎？有朋自远方来，不亦乐乎？人不知，而不愠，不亦君子乎？”
孔子说：“经常学习，不也喜悦吗？远方来了朋友，不也快乐吗？得不到理解而不怨恨，不也是君子吗？”
Mental processes exist because they have served life's continuance.
The music is my heart on a track.
The deepest problems in mathematics often arise from the simplest questions.
你无法改变过去，但你可以塑造未来。