one's heart is not in sth

/wˈɒnz hˈɑːt ɪz nˌɒt ɪn ˌɛstˌiːˈeɪtʃ/

/wˈʌnz hˈɑːɹt ɪz nˌɑːt ɪn ˌɛstˌiːˈeɪtʃ/

one's heart is not in sth

used to say that a person is not enthusiastic or passionate about a particular task, project, or activity, and is therefore not fully engaged or motivated to do it well