You might have noticed during the Ryder Cup that matches were won by the guys who held putts. When it comes to ball striking the best players in the world are all very good, fairways and greens. Where they get separated is on the greens.
Good posture is very important with the golf swing, do not think it is of no importance with the putting stroke. If you have bad posture your putting stroke will be more in the hands and not a pendulum movement from the shoulders.
When anxiety sets in you become stiff and this will result in you performing a jerky stroke. Control your breathing and visualize the ball going into the hole.
Staying down on the putt
Most short putts that are missed is because you are moving your body too much. Staying down on the putt means that you do not move your body too much or too early. "Coming out of it" is when you move your head early in the stroke to see where the ball is going. I have found that a good drill to help with this is to put your ball on top of a R5 coin and then hit the putt. Keep your focus on the coin for as long as possible after you hit the putt.
PGA Head Golf Professional