Say "I might have made a mistake" as there's always a non zero probability even if small that you actually have even if you believe 100% that you haven't.
Yeah because a bunch of people will read this and instead of realising this means their state of mind should be one of humbleness and respect for who is going to help you, and that's why you lead with "hey I made a mistake", they'll still feel like other people messed up and are dumb and an obstacle to whatever they need to do but will add "I made a mistake" as a first sentence "life hack". Usually you can tell if someone means it based on how they write or say the rest of what they need though.