Get a rubber mouse type mat or similar pad, put lens face down on it, apply a little pressure and turn.
The trouble with gripping the sides is its already tight without you distort the shape slightly to undo it![]()
As already said try rubber gloves, or I used the sidewalk of a car tyre, take the lens of the camera and put rear cap on lens and cap on body, press front of stuck filter against tyre and turn, the reason this works when rubber gloves don't always is due to the fact that you are not misshapping the filter by gripping it and squeezing. Just make sure you are pushing firmly against the tyre.
But, again, that won't work with a polariser (as per the OP) as the end turns independently of the filter body.
Not sure that will work on a CPL as the end piece rotates independently of the filter screw...
OP: Are you turning it, but it's not unscrewing or are you unable to turn it completely?

That's right, it turns but doesn't come off. So it's not too tightly, it just doesn't come off. I guess I'll try the tip of pulling and unscrewing at the same time.
Thanks though for all the good tips.
I loved the one about only using the lens on sunny days![]()
your not just turning the polariser at the end are you
just a thought![]()
That was my thought too.![]()
your not just turning the polariser at the end are you
just a thought![]()

Go on, admit it! You were turning it the wrong way all this time(glad it's fixed)

But the trick with pulling and turning at the same time worked, so problem solved.