sanguine
adjective formal uk/ˈsæŋ.ɡwɪn/ us/ˈsæŋ.ɡwɪn/
(CHEERFUL)
乐观的，乐天的
(of someone or someone's character) positive and hoping for good things
They are less sanguine about the prospects for peace. 他们对和平的前景不乐观。
See also: optimistic