Development
Nearly thirty years ago when I first started getting my paycheck from a church, I learn this quickly. Sure, I had no leadership responsibilities. I was answering phones and sending letters and postcards most days. But still, my Pastor knew I needed one thing if my plans for ministry were to be long term. He knew I needed development as a believer, as a person and certainly as a servant in ministry. On what was nearly his first week as my boss, he sat me down and recommended one book to start - Ordering Your Private World by Gordon MacDonald. He knew whatever God could use in ministry or even in His Kingdom had to be diligently and routinely tended to. The inner garden of my soul would parish without a habit of inner development. Ministry could be all giving and very little receiving without it. Tend to your soul and grow as a person and as a leader.
That pastor also taught me this - the only things that will make you a different person in 5-10 years are the books you read and the people you meet. I had never been a reader until that moment. I'll be honest - I was a writing major who flunked English Lit in college. I just hated to read. However, I loved to learn and I loved ministry. Both very good reasons to pick up a book. Also very good reasons to evaluate all your relationships. You become the average of your 5 closest friendships. Who is in your inner circle? Who gets your time and attention? Who are you allowing to speak into your life? It will change you, and if you choose wisely, it will change you for the better.
Disciple
Development isn't entirely inwardly focused. It also looks at others. Leaders know development is also about who you are pouring your life into. Who are you mentoring? Who are you training to replace you? Who will do what you are currently doing if you weren't there? Identify the "bright light" in your life - the person with the potential or skillset to work you out of a job.
Shallow and insecure leaders will never do this. They get too much self-esteem by being the only one able to or in-the-know. Those leaders are harmful to the organization when they leave, but even more so when they don't. Share what you know. Give your life away to someone you lead. Your role will only become more valuable, and you will become a better person from the constant challenge of bringing along someone on your journey.