Don't hold the pen too tightly. Find a pen and paper combination that doesn't require force to write. Ball point pens on cheap notebook paper are notorious for requiring too much force. On quality paper with a good pen the ink will flow effortlessly because of gravity and capillary action. You will only need a light pressure.

I'm left handed and I never really learned a good grip I could write with. So I've always struggled with handwriting. I also have an essential tremor in my left hand. As I have aged, the tremor has gotten worse. So now, I have to grip tight to minimize the tremor.

I've pretty much given up on handwriting, it's embarrassing to either try to write, or have someone else write stuff for me. I ask my wife to fill stuff out for me all the time, but people probably think that's weird when they see it.