In gaming, trigger discipline is when one holds his/her gunfire while hiding upon seeing an enemy player walk by him/her in order to see if there are more enemies following the first player/catch the enemy off guard. It requires incredible patience and self control to not open fire on the first enemy you see since there could be more behind the first enemy walking in hence the discipline part of the term.
My buddy was able to get an Ace in Valorant with a very nice display of trigger discipline and catching them off guard.
The practice of dedicating oneself to the truth, delaying gratification, accepting responsibility, and having the capacity to plan for the future as well as being able to live in the moment.