According to me, Courage is nothing but stepping out of your comfort zone and doing something you have never done before or taking accountability of your own actions (example of being courageous). Without getting too philosophical, it merely goes to say that the more you do that the more you step into your learning zone.
When you step out of your comfort zone, you feel the discomfort of doing something that is either new or still a learning for you. Like learning to ride a bike or drive a car, it takes practice. The more you do it, the more skilled you become until eventually it becomes something that is in your comfort zone.
Start by believing in yourself. I’m sure there are some situations where you are courageous or have been in the past. Children are often courageous. They ask bold questions, do what they think and feel is right in every moment. They don’t worry about what might happen.
As for leadership, it is a practice. For instance, Olympic athletes don’t hope to get a gold medal just by turning up on that same day. Similarly with leadership, you need to practise and fine tune your leadership capabilities. That requires courage to stay when it’s uncomfortable and not easy, in the hope that what you are doing matters and makes a difference. If it doesn’t matter, then have the courage to stop wasting your time and energy on it and do something else instead!
Eventually you become effective as a leader only when you step into your danger zone when you’re courageous so you know where your boundary lies.