Mistakes happen. In order to repair the damage done by mistakes, you need to apologize with out excuses. That means no and's, if's, or but's attached to your apology. Even if you have a legitimate reason for doing what you did, for an apology to be conveyed as truly sincere, you much leave off the excuse.
Leading people is vastly different from working as an individual contributor. Download our latest guide to make the mental leap to leader: