Did you know that just like you are left- or right-handed, you are all left-eared or right-eared, and left-eyed or (more usually) right-eyed? The ear thing is easy: what ear do you hold your phone to? For me, left – for most people, right.
And the eyes? How do you know?
Find a small object some metres away. Then cover it with your thumb held up. Now hold that thumb, and alternately close left and right eye. You will see ONE eye has the thumb in front of it. For most people, this is the right eye. For me, the left.
Why is this important? because it also affect the way you hold your camera. I use my left eye on the viewfinder. You probably use your right eye. And if you use your right eye, make sure your left eye is closed. I do not have to do that, since my “other” eye is behind the camera. I prefer it that way!
Since you are left eyed and use 1Dx bodies, you should check out Joe McNally’s video “Da Grip”: https://www.youtube.com/watch?v=EDsx3-FWfwk
If you are right eyed you can learn to keep both eyes open which will give you a view of the whole scene (well the left side of the scene anyway), and a view through the viewfinder. In some cases this is a useful ability.
Some people are ambidextrous. So are their eyes. One is slightly dominant but they can use either equally well with very little practice.