To make a sudden, small movement because of pain or fear. (Cambridge Dictionary)
To withdraw or shrink from or as if from pain: Wince. (Merriam – Webster)
If you flinch, you make a small sudden movement, especially when something surprises you or hurts you. (Collins Dictionary)
If you flinch from something unpleasant, you are unwilling to do it or think about it, or you avoid doing it. (Collins Dictionary)
Make a quick, nervous movement as an instinctive reaction to fear, pain, or surprise. (Oxford Dictionaries)
Avoid doing or becoming involved in (something) through fear or anxiety. (Oxford Dictionaries)
Ha! Made Ya Flinch!
Stopping the flinch: getting serious about core control.