Mistakes happen for concrete reasons. A student didn't memorize all the requisite facts, didn't execute the steps of a process, or perhaps just ignored the directions. The red "X" is just a simple assessment of the actions that student took -- actions he or she can easily fix next time. Sharing that clarity and causality with your students is the best way to teach deliberate practice, instill motivation and help them develop a more constructive relationship with mistakes.
Find the reason why you made a mistake.