Being a CEO can be a lonely job–there is no obvious person in whom to confide. Keeping a journal can fill that void, by giving a new leader a chance for structured reflection of recent past events and decisions, and mental rehearsal for future ones. Despite the time and discipline it takes to keep a journal, it should be part of every new leader’s toolkit.

Read more here https://hbr.org/2017/07/the-more-senior-your-job-title-the-more-you-need-to-keep-a-journal?ab=HP-hero-for-you-text-1