Nadal is a great player, but he exhibits classic obsessive compulsive rituals to calm himsel and to feel right. He evens things up.so his brain can feel balanced.
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He pulls on his underwear, wipes his arms, then his face, touches his shoulders, then his eyebrows, cheekbones, then his ears. ...
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This is clearly O.C.D. and it probably calms him. He also must use 2 towels and place them on his deck chair with racquet on top.
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Perhaps a serotonin uptake inhibitor would help him by re-balancing his brain chemicals. Also some adjunct talk therapy to get soem feedback from a professional would help his anxiety, and feelings of incompleteness.