is there a difference between left and right ear?

[careful]

I've noticed that when i'm at my computer listening to music, or whatever else, with full ear headphones, sometimes i take one phone off my ear and shift it so that only one ear is covered, to free up my other ear so i can listen to the external environment. i do this mainly because i don't like to be in a state where i can't hear anything going on around me (makes me anxious), but whats weird is i do this almost every time i'm using the headphones and i always take off the left phone while leaving the right phone covering my right ear. i'm pretty sure i make a near conscious decision to take off at least one phone when i begin to feel it necessary, but automatically i take off the left without further thought, its just the ear i always chose to free up. can anyone explain why i developed this habit? does this suggest the auditory perception of my left ear and right ear differs, or did i just develop an arbitrary habit of freeing my left ear when i first started using headphones extensively and now continue to do so for the mere sake of consistent habitual action?