To lead well you need sound judgment -of market forces, of problem areas, of money, and most importantly of people. Other than lack of correct information, your judgement can get clouded by your emotional baggage.
If you have been let down by people, it is likely that you will view someone approaching you with suspicion, even if if the person might be having a nice proposal or an idea. If you are carrying a feeling of superiority based your past achievements you might fail to notice valid criticism of your point of view. If a feeling of being passed over in case of job promotion keeps bothering you, you might try too hard to succeed or you might simply give up trying.
Leaning leadership involves learning to know about your emotions and learning to deal with them. A good learning program has ‘shedding emotional baggage’ as a vital part.