плохому танцору и яйца мешают

Etymology
lit. 'a bad dancer is impeded even by /his own/ balls'. The real etymology is about eggs, not balls and goes back to the time when the German egg dance (Eiertanz), a traditional Easter game, was popular, in which eggs are laid on the ground or floor and the goal is to dance among them damaging as few as possible.

Proverb

 * 1) a bad workman always blames his tools