depends on the person themselves; up to the individual
Used to say that an outcome, decision, or effort depends on the person in question, not on external factors.
成功できるかどうかは本人次第だ。
Whether you can succeed depends on you yourself.
やる気が出るかどうかは本人次第です。
Whether motivation comes or not is up to the person themselves.
Similar construction but uses 人 (person) instead of 本人 (the person in question). 本人次第 emphasizes the specific individual involved.
Suffix meaning 'depending on'. 本人次第 is a specific compound using this suffix.
Compound of 本人 (the person himself/herself) and 次第 (depending on). The suffix 次第 conveys that something is contingent on the preceding noun.