The friendships we have at work influence us to stay in that place (or to leave). If someone's best friend at work leaves, leaders shouldn't be surprised if that workers resigns next.

The solution: Look for ways you can support the employee that's still there. You have to think: "How can I have more of a dialogue with those individuals who might get left behind, and how can I help them adjust to that transition?"

When one employee hands in their resignation, other workers inevitably face an increased workload at least temporarily--or more permanently if the employee who departed isn't replaced.

It's important to have conversations about workload--people feel it the most if they're not getting recognition for the extra work they may have taken on, either through title or pay. Be transparent with workers about the backfilling process. If it isn't a priority to fill a vacancy, then be willing to compensate the employees who are picking up the extra slack.

Employee investments contribute to a positive company culture, and especially in a time when many workers are reevaluating their career choices, upskilling opportunities can make a big difference in retaining them.