Hand and finger cramps happen to me all the time, it makes getting things done a problem at times...
tEN wOLVES
I'm 49 and in pretty good shape - I'm an Army Reserve drill sergeant and still well above the drill sergeant standard on my PT test. I get hand cramps and soreness every time I work on anything as big as a holster or belt project.
Here's my latest one - a holster for my .44 Magnum old model Vaquero, to carry on hunting trips. I made it thicker than usual and using the fancy engraved Chicago screws at each end of my stitching is a new idea I had that seems to work pretty well. This is also the first black holster I ever made and the first with black thread. The loop is a layer of the holster lining leather, laminated to a layer of fake python skin, printed on cowhide (even feels like snake skin) that I got at Tandy.
Still working on the belt.