There is always a temptation to obfuscate or couch everything in legalese—to say “mistakes were made” but never admit they were yours. This will not work. People will figure it out. And they will be pissed. If something is your fault, tell them what you did. Tell them what you’ve learned from it. And tell them how you’ll prevent it from ever happening again. No evading, blaming, or making excuses. Just accept responsibility and be a grown-up.
