Even if you aim perfectly to allow for the exact break of a putt if you then roll your ball too fast it will miss above the hole. And if you roll it too slowly it will likely miss below the cup.
Now I know that some golfers like to take practice strokes (which can become good preview strokes) behind the ball while others take them right next to the ball (while in their setup position).
You need two things to make breaking putts: 1) a stroke that starts the ball on your chosen line and 2) the correct amount of speed so the ball can hold that line all the way to the cup. Good line good speed—nailing one isn’t enough.