[take] a look in the mirror

to reflect on one's actions so as to accept one's flaws and shortcomings

The origin of the idiom "take a look in the mirror" is not rooted in a specific historical reference, but it draws upon the literal act of looking at oneself in a mirror as a metaphor for self-reflection. Mirrors have long been used as tools for self-assessment, allowing individuals to see their own reflection and gain a visual representation of themselves and this expression's usage captures just that, but in the case of self-evaluation.

After the disagreement, he decided to take a long look in the mirror and assess his role in the conflict.
It's time for the company to take a hard look in the mirror and address the issues affecting its performance.
When faced with criticism, it's essential to take a long look in the mirror and consider how valid the feedback might be.
If you think I'm the one holding this complay back, maybe you should take a look in the mirror sometimes.
As a leader, it's important to take a hard look in the mirror and evaluate the impact of your decisions on the team.