While a tripod is pretty ridged, there is no comparison to a bench set in concrete with a decent front rest and a butt bag. At a bench your elbows are also supported thus supporting your upper body. With a tripod you are not supported and the rifle has only one support point compared to two on a bench.
Practice, practice, practice, when we had Egg Shoots I'd get out and start with the 22lr off of sticks and when I could start keeping rounds in the dot I'd move to my centerfire rifle, lots of dry firing to learn to control my trigger with the movement of the reticle on the target. Lack of sleep, too much coffee, all would affect how I was shooting.
It makes little difference how the other guys do. Someone might have nerves of steel and shooting off of a tripod is something that just comes easy for him, you can't compare yourself. You can only do the best you can and then keep your shots within your ability.