Dartitis is a condition which can affect darts players, and severely damage their performance. It can be compared to 'the yips', an expression used to describe apparent loss of fine motor skills without any explanation. The term is used in reference to players who struggle with some kind of psychological problem with their technique and/or release of their darts.
Dartitis: The condition where you try to throw a dart - but can't
The psychological condition stops players from releasing a dart.
BBC News