Dysfunctional leadership creates a self-sustaining cycle where employees vying for promotion mimic the toxic behaviors of their boss. They do this to endear themselves to the decision-maker, believing that demonstrating a better leadership style would disqualify them from the role.

Promoting top individual contributors into management often backfires. Their competitive nature, which drove individual success, makes it hard to share tips, empathize with struggling team members, or handle interpersonal issues, turning a perceived win-win into a lose-lose situation.

When diagnosing a failing department, stop looking for tactical issues. The problem is always the leader, full stop. A great leader can turn a mediocre team into a great one, but a mediocre leader will inevitably turn a great team mediocre. Don't waste time; solve the leadership problem first.

Early leadership mistakes often stem from a perceived need to have all the answers. A more powerful approach is to express confidence in the mission while openly asking your team for feedback on how you can improve as a leader to better serve them and the company.

The desire to be a popular boss is a trap. Prioritizing being liked often means avoiding boundaries and tough feedback, which creates an unsafe, unproductive environment. Leadership requires earning respect by providing clear direction, setting standards, and trusting your team—which is what they actually value.

A mentor's unique value lies in their ability to provide brutally honest feedback that a regular coworker would avoid. This directness, like being told your thinking is 'all over the place,' is what forces critical self-reflection and sparks genuine growth.

A common pitfall for new managers is seeking validation by being liked. A great leader's role is to provide constructive challenges and uncomfortable feedback, which fosters genuine growth and ultimately earns the team's gratitude and respect.

Not all leaders are inspirational. MongoDB's Cedric Pech suggests that while great managers show you what to do, bad managers offer an even more visceral lesson: what to avoid at all costs. The pain from working under a poor leader creates a powerful, lasting template for the kind of leader you never want to become.

To truly understand a business, leaders should spend time in a non-scientific, operational role like IT. This 'back of house' experience provides an invaluable perspective on how an organization functions, what other teams value, and the real-world impact of change, creating a more empathetic and effective leader.