When standing over a putt there are two things most people are thinking about: speed and direction.

In long putting, speed generally is more important. Pick the line either by lining up the words or picking an intermediate target and then make sure that you are totally focused on your distance control.

Distance is controlled through our eyes, therefore it is critical that we rehearse our putt looking at the hole not at the ball. A pre-shot routine is mandatory to relax us and make sure that we are doing things that we practice.
My suggestion would be to take care of the line, set up to the ball, take two or three practice swings while looking at the hole, set the putter to the ball and commit to what you rehearsed. The distance image will stay in your mind -- your job is to trust what you just saw!

No changing the plan!!!

Work on your pre-shot routine in a practice environment so you are ready and comfortable to use it on the golf course. Remember to trust what your eyes tell you and those 3-putts will be a thing of the past!!!