Hold the jar tightly in one hand and firmly punch it’s bottom side with your fist or wrist. You should hear a distinct sound somewhere between hissing and popping. Afterwards the jar is easier to open. Repeat, if necessary.
Be sure to hold and punch the jar in such a way that you do not break your own fingers but at the same time do not lose your grip on it. As a further safety precaution, place a blanket on the back of the jar to avoid slicing your hand in the unusual event that the glass breaks.
My personal guess is that this somehow briefly lifts the lid and thus allows for an adjustment of pressures. However, I remember having heard a university lecture on this which involved gases dissolved in liquids contained in the jar, but unfortunately I fail to find any publications or other sources on this.