If you have difficulty looking people in the eyes, you are not alone.
There is often an intensity when looking someone in the eyes that makes us feel simultaneously invasive and vulnerable. This is why holding one’s gaze helps with bonding by heightening one’s connection to the other person.
Some scientists from Kyoto University have discovered that maintaining eye contact while processing what a person is saying is sometimes taxing on the brain. I would wager to say that this is especially true of introverts who are much more internalized than externalized.