Your grip is the force that you put on something. There are many tools we grip firmly. An example of this is your car steering wheel. Why do people grip it so firmly? Why do we put so much stress on the shaft of a pencil? What about our utensils while we eat? It might be a habit. Pay attention to how you grip everything, you may notice that you grip tightly when there is no need. This is causing unnecessary stress which is negatively affecting your carpal tunnel. Try to consciously relax and not exert so much force with your hands and fingers. Take a few deep breaths and release some tension while you grip. If force is required, divide the load between your entire hand; do not exert all of the force on your palm.
Another useful tip would be to invest in tools that have textured grips, which would give you a little more resistance. For writing, go for pens that enable smooth and flowing writing and only need a little force. If you are working with your hands on something that is elevated above you, it is putting more stress on the tendons and muscles in your hands. Try to put yourself on the same level by using a stool or a ladder. Also, use gloves to improve your grip and save your hands from absorbing shock.
Extra tip: Always keep your hands dry. Sweat reduces grip. Focus on the object you are gripping. Mostly, the fear of losing the object makes us to grip it tightly. Focus can ease this fear and improve your grip.