Opening jars: what's making it hard?

Quick answer: Opening jars gets hard for different reasons — using one hand or weak grip — and the tool that helps is different for each. Pick the one closest to you.

Opening a jar quietly relies on one hand holding the jar still, a hard twist from the other, and fingers that can close around a small lid. The hardest moment is the first quarter turn, while the vacuum seal is still holding; after that the lid usually spins freely. If you only have one hand to work with, the problem is holding the jar. If both hands are there but the grip isn't, the problem is force.

Which is closest to yours?

I can only use one hand Opening jars with one hand Brace the jar so it can't spin, between your knees or trapped by a drawer, then twist the lid with your free hand.
My grip is weak or my fingers hurt Opening jars with a weak grip Break the vacuum before you twist: lever the lid's edge up with a spoon until it pops, then turn it with your palm through a rubber glove.

None of these sounds like you? Start from a condition instead, or pick a different task.