Consistency

How I play has much to do with my state of mind at the moment.  If I am patient and actually trying and seeing the entire board, I do pretty good 

If I am tired, bored and impatient trying stupid stuff without thought, I do pretty poorly.

Great chess players must not go through these ups and downs in state of mind.  They must be rather like a machine.  How do you stay consistent in your mind set?

All chess players have ups and downs, even strong ones, because they’re human too. Look at any titled players games, on this site or their federation/FIDE rating history, it’s up and down. Many titled players earn their norms and rating for that title briefly mid tournament and it falls afterwards, never reaching that rating again. All players have small ups and downs with a gradual incline, an eventual peak and or plateau, then decline, until they hit their rating floor, or quit before that happens. Stronger chess players are just more consistent with understanding this and knowing when to study, when to take a break and when to push through it. 

The very top players must a gift for mental stability. To gain the title and keeping it demonstrates a mental control most people do not possess.

Now that I recognize when I am in a mess around and lose mood...I can just stop playing.

Even when they feel bad, their "autopilot" (their trained thinking process) still carries them to a decent level.