やる気 - will (to do something), motivation
In the same line, there is やり甲斐 (being worth doing), a word which I learned @Haru さんのおかげさまで, through the reading of Haruna’s daily diary (reading practice) (これを教えてくれてありがとう!).
This word is ‘family’ with 生き甲斐 (purpose in life, raison d’être) as well as other 〇〇甲斐 words for expressing that something is worth 〇〇 (言い甲斐, 話し甲斐).