The best advice used to be to write your move down before you play it, and take a few moments to look at it fresh from every point of view. Unfortunately that became illegal when some players began doing it as a way of getting approval from stronger players. It is still a good idea if you only pretend to do it. During the recent candidates it was interesting to watch live video of these top players. Even when put in check with only one legal move they never moved instantly unless in time trouble. They seemed to be telling themselves "Never move instantly!". Some players often do move quickly to intimidate the opponent, or not to give away that they are surprised.

I recommend watching videos to observe the board habits of GMs. Try to guess what they will play. Does it look like an easy decision or a hard one? Can you predict how long they will take? Can you tell from their eye movements what they are looking at? Can you imitate their manner? This might address some of your problems.

The best advice used to be to write your move down before you play it, and take a few moments to look at it fresh from every point of view. Unfortunately that became illegal when some players began doing it as a way of getting approval from stronger players. It is still a good idea if you only pretend to do it. During the recent candidates it was interesting to watch live video of these top players. Even when put in check with only one legal move they never moved instantly unless in time trouble. They seemed to be telling themselves "Never move instantly!". Some players often do move quickly to intimidate the opponent, or not to give away that they are surprised.

I recommend watching videos to observe the board habits of GMs. Try to guess what they will play. Does it look to you like an easy decision or a hard one? Can you predict how long they will take? Can you tell from their eye movements what they are looking at? Can you imitate their manner? This might address some of your problems.