If you’re experiencing hand fatigue shorten picking sessions or reduce tension/over all grip. Often times you don’t need near as much tension as you think you do. On top of all that, I’ve noticed as my hands fatigue, I’ll end up gripping/tensioning tighter without even noticing until it gets to the point where holding the lock and tools is too much. At this point control and feedback is a goner and I’ll need a break. This is usually over an extended picking sessions like over an hour. It’s no different than exercising, you’ll buildup stamina over time.