People leave jobs. If you are a manager, people will leave your team, just as someday you will leave your team.
When this happens it’s an opportunity, a chance to re-evaluate. While you might want to immediately pull out the job description that you used when hiring for the role last time, instead, take some time to think.
A chance to learn
When someone that works for you tells you that they are resigning, it can feel personal: ‘they don’t like working for me.’ It can hurt. You might immediately look for any reason why it isn’t your fault.