Mental mistakes do not exactly exist. Our mind will always do what it supposes the best possible thing to do. However, apparently, a mistake mind makes, might be to relentlessly replay the past and the what-if scenarios. It does this, once more information is available. This is not fair on the ego and will seriously undermine the self esteem. The mind really did what it thought to be the best thing to do with the available (but limited) information in that past.
Emotional mistakes do not exist either. You feel happy, sad or neutral. There is nothing one can do about it. Mind can prolong sadness or happiness, by focussing on the fleeting emotion and keeping it alive. Perhaps this game of mind, playing with emotions, can also be seen as a mistake by mind.
But replaying past and what if scenarios, or staying with the emotion is part of the learning process mind has to go through before it will finally discover that this is not the best thing to do.
Further up the learning curve, mind will finally discover that Silence is important. Again, not listening to the Silence is part of the learning process that mind chatters us through. When it discovers that a tennis ball can also lay still on the tennis court, the learning process of mind can go one step further, first identifying with Silence, and soon not identifying at all any more.