A great way to develop as a leader is to practice. Yes, literally practice.
For example, if you have found that you struggle being courageous in meetings, find some low risk opportunities to speak up. Practice.
Or, if you just go along for the sake of getting along, find a low risk opportunity to challenge the status quo. Practice.
Or, if you doubt yourself and defer to others, sit up straight and look the part unit there is no doubt. Practice.