Snap Caps are a good way to protect the firing pin. Dry fire is a good practice point when ammo is in short supply.
Get yourself a shooting stick - primos trigger stick is a good one, makes a world of diff with offhand shots. As stated the sling is useful too.
Doing jumpnjacks or burpees or whatever you want to do to raise you blood pressure, adrenaline, etc. might cause you to start down a bad habit road w shooting - IMO, do your dry firing with snap caps, use a 22 or BB gun but understand neither of those is as accurate as your rifle, and figure out how to control yourself when you see something.
We spend way too much time and energy and money to play this game - no sense missing or making a bad shot cause you are shaking like a leaf.
Another thing is strength in holding the gun up. I'm old and shaky some of the time. The shooting stick helps, so does doing pushups and exercising. I'll shoot offhand inside 100 yards, will use stick out to 250 yards if I can rest my right elbow on something, if not, then 150-175 yards for stick.
One of the deer I shot this year was running about 50 yards out thru a swamp - 4 shots in a "10 second" period, all aimed and most absorbed by trees - was tracking it thru scope and hit the trigger when the deer hit an opening while staying on the vitals. It always amazes me how muscle memory takes over during times like that. Never came off gun, never lost sight of deer, was almost like I had done that before.
Your practicing will make a difference in what happens in the field.