I have this tool called a strap wrench in one of my kitchen drawers.
It has a plastic handle with a long strap of rubber the comes out and then circles back into the handle. You can adjust the length of the rubber part to whatever size you need, and it really comes in handy.
Normally, a strap wrench is used on pipes or other plumbing applications, but I’ve found that it works very well to open those jars and lids that are impossible to open with your bare hands.
I used to take a butter knife and bang on the lids to try to loosen them, but that only worked sometimes, and if I slipped, I would hit the glass jar and break it.
So now I just grab my strap wrench, wrap the rubber loop around the lid, tighten the loop and then twist the lid right off. It works every time, and there is no danger of breaking your jars.
You can find a strap wrench for less than $5 in stores like sears, walmart, target, etc. Pick one up the next time you’re out shopping!