I think that the most important thing a leader can do is to forgive the people he leads the mistakes they make.
The importance of forgiveness lays in the fact, that it sends the message that rules are not there to punish. As a leader you want you people to follow the rules. You do not want them to be so afraid of the rules, that they start to avoid them.
To forgive someone the mistakes he makes, does not mean that you let it be. To forgive does not mean letting the mistake pass as if nothing happened. Forgiveness means giving the wrongdoer the chance to admit guilt, but then letting go of his guilt.
To forgive also means that you sit down with the person who made the mistake to help him understand what went wrong and what his part was. It also means helping the wrondoer to find a solution, to prevent the mistake from being made in the future.
And of course it is much easier to fire someone who makes a mistake. But then you will have one certainty. In the end you will have less and less people to fire and hire. And the persons who work for you, will be less willing to take risks. Because if there is one thing clear of the social systems in which humans live it is the following. In a surrounding in which there is little tolerance for mistakes, every new participant is taught that making mistakes is not tolerated and should be avoided. And the best way to avoid making mistakes is to do nothing. And the second best way is to do your work the way it has always been done, by eveyone before you.