I recently made a mistake. But as soon as I understood what had happened, I notified my customer with the explanation and the action plan to avoid the same mistake in the future.
My colleagues were a bit hesitant on informing the customer. After all, no real harm was done. At most, the result was less optimal as it could have been, and chances were that the customer would never have noticed. I could understand this reaction as I remember the time when I would have reacted the same way.
It’s probably even a human and natural reaction: the child realising it did something wrong quickly assesses if its parent or teacher is going to find out, and then decides the strategy to “cover up” or to start crying.
But by getting older, you understand that most “mistakes” are often just wrong choices or decisions made at a certain point in time. And if at that time, all the inputs and all your knowledge pointed at the decision you made, there is nothing to feel bad about.
Instead it is better to share your experience as broad as possible not only to help yourself but everyone around you (including that customer) in creating a better decision process.
If you keep this mindset, also in your communication, a mature customer will appreciate your action and will learn and improve together with you.
And if you have a customer that only knows the “blaming game”, remember that the only people that don’t make mistakes, are the ones that don’t do anything. But then I would consider thát their biggest mistake of all.