i had similar stuggles at first, sharpness is first, test it on your thumb nail it should have a decent bite, second water, i dip my blade in water for a roll, not each piece, the other is when u dampen the nori to seal it, dont overwet it. then if possible, allow it to sit for a bit maybe 15-30 seconds, with the sealed area on the bottom, that will help alot. if youre in a rush to get a hosimaki or futomaki out (nori on the outside) then when cutting position the roll in the direction u will finish the cut, so as you pull towards yourself to cut the final bit of nori u pull it tighter, hopefully that makes sense.

I had similar stuggles at first. Sharpness is first, test it on your thumb nail - it should have a decent bite. Second water, I dip my blade in water for a roll, not each piece, the other is when you dampen the nori to seal it, don't overwet it. Then, if possible, allow it to sit for a bit, maybe 15-30 seconds, with the sealed area on the bottom, that will help a lot.
If youre in a rush to get a hosimaki or futomaki out (nori on the outside) then when cutting, position the roll in the direction you will finish the cut, so as you pull towards yourself to cut the final bit of nori, you pull it tighter.