知之为知之，不知为不知，是之也。

we say, 此起彼伏。got here up there down. many things go in this cycle. juz look at waves. oso got up got down. got crest got trough.

易经 is a good book about cycles. but unfortunately.... i too lazy read it fully. AHHHH. nvm. when i got too much time for myself then read.