Golf is a game where the ball is stationary, giving you time to prepare yourself for the shot. However, many golfers develop a counter-productive habit of negative talk when they stand over the putt.
Instead of multiple swing thoughts, focus your attention on visualizing the pathway of the ball until it drops into the hole. This will distract you from negative thoughts and allow you to concentrate on getting the ball to the target. It also helps to release tension from your body, promoting a smooth putting motion that gives you the highest chance of making the putt.
It only takes a few seconds to visualize the putt you are about to make. Start with an assessment of the way the ball will break towards the hole. Will it be a straight putt or one that curves left or right. Instead of having just a general idea, you want to view the entire pathway of the ball as it leaves the putter face. This might require a bit of imagination but try to visualize a pathway the width of your golf ball. You want to see the ball rolling along this path and dropping into the hole. As opposed to a straight putt, the slope of the green will make your ball curve towards the hole. So for breaking putts, pick out the highest point on the pathway and aim towards it. Watch the ball slowly turn towards the hole once it passes that point. Pay attention to watching the ball finish inside the hole because that it is the ultimate goal.
Commit to visualizing every putt, even on those short 3 footers because they don't take much break and are the easiest to start with. There is something about visualizing a putt and then actually watching it drop into the hole that helps to build up your confidence as a putter. When you picture exactly what the ball will do as it gets to the hole, you are able to compare your plan with the actual outcome. If the ball rolled exactly as planned, good job. But if it didn't, you should assess where the problem lies.
Remember to stay relaxed and do your best every time. It might take some time before visualization on the green becomes second nature to you, and might even be difficult to do so in the beginning.