Also if you have the swivel knife in a 'Vulcan death grip' it is only going to add to your fatique. Make sure the knife sharpened and honed so that it cuts smoothly and easily. If you're have to grip it a lot so you can drag it acoss the leather it needs sharpening. strop it A LOT. cut, cut, cut, strop, strop. rinse and repeat.
Cheers!