Not being able to open a jar can be frustrating, but struggling with one that you've struggled with before is even worse. Prevent this by dabbing a little petroleum jelly on a jar after you've opened it the first time. Image from turnerburns.
If you've got a jar full of something sticky (like jam or sauce), it can get into the jar's threads and make it difficult to open later. Smear a little petroleum jelly on the clean threads of the jar so you don't have to struggle to open it every time. If it's not obvious, use only as much as you need so excess jelly doesn't end up inside the jar.
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