Definition
To assume the responsibility of doing something without being asked or required to do so.
主动承担做某事的责任，未经请求。
She took it upon herself to organize the event, even though no one had asked her to.
她主动承担了组织活动的责任，尽管没有人要求她这么做。
He took it upon himself to clean the office, much to everyone's surprise.
他主动打扫办公室，让大家都很惊讶。
When the manager was away, she took it upon herself to manage the team.
经理不在时，她主动承担了管理团队的责任。