Why is one muscle bigger than the other?

Ok I'm right handed, but my left side of my body is more ripped than the right. My left tricep is bigger and mor cut than my right, my left calf is more ripped and has a better shape than my right one. But when I lift weights i could lift the same in both arms like tricep extensions, but when I work out my triceps it always feels like my left one burns more than the right on(left is bigger one). Even when I do chair dips I still feel it more in my left one. Why is this and how do I fix it