A Definite Chief Aim

The first law of success is to have one chief goal and to work towards that goal. Among the virtues of this kind of thinking, is to eliminate distractions and doubts.

I recall the advice from the chess book Think Like a Grandmaster, by Alexander Kotov that one should analyze a candidate move completely and then go on to the next. Once one has analyzed all your candidate moves and the opponent's responses to that, then settle on the move you choose. If you have time, check and double-check your analysis but do not keep going back and forth while you do.

Then make your move and stick to it!