The full sentence is:
何{なに}もかも手{て}にした気{き}でいたんだ
For now I think 何もかも手にした comes from 何もかも手にする 'to obtain just about everything / almost everything' but I can't understand the purpose of the rest and how it changes the meaning of the phrase.
Japanese Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the Japanese language. It only takes a minute to sign up.
Sign up to join this communityThe full sentence is:
何{なに}もかも手{て}にした気{き}でいたんだ
For now I think 何もかも手にした comes from 何もかも手にする 'to obtain just about everything / almost everything' but I can't understand the purpose of the rest and how it changes the meaning of the phrase.
~~した気でいる means "to (keep/stay) think/imagine/feel(ing) that one did~~". (≂ ~~したつもりでいる) (cf. 「~~した気になる」 "to think/feel/imagine one did~~", 「~~のつもりでいる」 "to fancy oneself as~~")
何もかも手にする means "to gain/obtain (anything and) everything".
So 何もかも手にした気でいたんだ literally means "I thought/imagined that I had obtained everything."