Many performance reviews ask for a component of employee self-assessment. This will be a document that asks if you have fulfilled your core role responsibilities and achieved agreed KPIs over a specified period, and to what extent you did or did not fulfill these.

If your employer does not require self-assessment, consider writing something independently. It is a valuable exercise for you and will provide more information for your manager to determine eligibility for benefits used to reward exceptional performance, such as salary increases or promotions.

Being honest in these assessments allows you to talk openly with your manager about the areas you have succeeded in, and the areas that require attention or improvement. It will make you more receptive to constructive criticism, and able to implement suggested changes and strategies both quickly and effectively.