It's vital that the children learn about exam technique. Part of that is indeed, learning how to cope on the day with something you feel you've done badly. In our competitive sport, we have to learn to forget what has passed in a previous round: if we feel we've done badly, then it can't be allowed to influence how we approach the next round. Over the years, both DD's have learned how to forget what has passed and move on. Despite having an in-built fear of failure, they were able to transfer their sport mental-skills to the 11+ approach. In Essex, we have three papers, with the most important coming right at then end - DD dreaded the first one the most and she learned to ignore how she felt about it, to avoid jeopardising her chances on the others.
We also encouraged our DD's to embrace mistakes - they help us to improve and grow strong. Mistakes are good.
She had something she could use if she felt anxious - she would twist her left earlobe anti-clockwise to "switch the panic off" and twist the right earlobe clockwise to "switch the brain- juice on", so it would flow down her right arm to her writing hand
Worked everytime because panic interrupts the flow of brain- juice!