The trigger should be a motored responce, i.e a message to your brain to move your finger in responce to you seeing as good a sight picture as you can get within the capabilities of your hold.

The best way you can achieve that is to totally concentrate on the aim, that is the sight picture, the correct alignment of the foresight in the rear sight, as central and the tops level, with that picture placed in your ideal place on the card, often just under the aiming mark, or lower if you wish. Your visual focus should be on the foresight whilst judging that picture and its allignment. The more you concentrate on that the less available concentration there is to be diverted to unwanted trigger thought.

You should never even think about the trigger, just let it happen, when you train, dry firing or shooting, work on hold and aiming, if you wish to train trigger, separate it from either dry or live firing. Just sit with your trigger on dry, and continually operate it in the process you would take with a shot, take first stage, hold, and increase to take the trigger. When you shoot or dry fire, take the first stage as you first cross the aiming mark on your lower, then as you finalise the aim its ready to go, and it more likely to be a motored responce. If you take the first stage after you have refined the aim you are A) wasting valuble hold time, B) redirecting concentration back to the trigger.

From the settling of the aim the shot should go in 6 to 8 secs or reject and start again, it will not get better.

Have fun,
Good shooting