orchid hatch
You are likely continuously holding tension in your arm.
For the majority of aiming you want to keep you keep your grip relaxed, given that tension adds nothing in terms of stability. It only reduces range of motion and can cause fatigue/pain.
The only time where you do use short bursts of tension is when you need speed, like with flicking, given you cannot generate speed without some form of extra tension. So be mindful of that for your future runs.