Write Down Your Accomplishments
When it comes time to do performance reviews you will be asked to provide some sort of write up about what you actually did. So you should know what you've done.
Don't expect your manager to remember all the great stuff you've done. Don't even expect to remember it all yourself. It can be very easy to forget the details of how you spent your time and going back to look at all the PRs you merged over the past 6 months probably won't tell the whole story.
Keep a running document of the things you've accomplished. This can be projects you completed (complete with metrics that show what your completed project actually accomplished) and bugs fixed. This can be internal tools you've written that have saved the team time. It should also include time you've spent mentoring other people or serving on committees or giving talks. Include links to PRs, documents written, dashboards that show improvements you're responsible for, etc.
When it comes time to write up what you've accomplished during the last review cycle, you should be able to just start with this accomplishments document as an outline. Julia Evans goes into great detail about how and why to build this record in her post about brag documents.