樂天知命

乐天知命
lètiānzhīmìng
to be content with what one is

CEDICT

to be optimistic and content with life

Wiktionary

順應天意的變化，固守本分、安於處境且悠然自得。語出《易經．繫辭上》：「樂天知命故不憂。」《儒林外史．第八回》：「近來我在林下，倒常教他做幾首詩，吟詠性情，要他知道樂天知命的道理。」也作「樂天安命」、「知命樂天」。

重編國語辭典

Entry Composition

1 樂天 lètiān
  1. carefree
  2. happy-go-lucky
  3. optimistic
2 知命 zhīmìng
  1. (literary) to understand the Decree of Heaven; to know destiny
  2. (literary, idiomatic) age of fifty
  3. age of fifty
  4. to understand the Decree of Heaven; to know destiny