Hold the jar firmly in your right hand and twist off the lid with your LEFT hand. This is a more natural movement than twisting anticlockwise with the right hand and more likely to succeed.
Alternatively, hold the lid firmly in your left hand and, with a rubber glove on your right hand for added grip, twist the JAR clockwise and it should open. (This method works well for champagne and sparkling wines, too. If you don't want to waste half your bottle of bubbly with it frothing all over the place, grip the cork and gently twist the bottle. A discreet little phhhht and it's open with no overflow!)