Autism

Neurotypicals try to properly explain what you were doing by instinct.

Jokes aside, I like the idea that Joel is trying to get to: the most tolerant society would be one that just accepts without a second thought that some people simply have a different form of innate non-verbal language.

For people who actually need some explanation about eye contact: most human brains are wired to interpret information about other people's intentions from their facial expressions (including many autistics), so by looking at other people in the eye, your brain attempts to work the "puzzle" out, and also becomes aware that the person looking at you is trying to read you. If you're insecure, that will make you feel vulnerable. If you're unused to making eye contact, your brain will get tired fast because it keeps trying to process information without knowing how.

The truth is that it's a generally unreliable communication tool except for very clear cases, and its main utility is triggering other people's pattern-seeking to make them see you as just another normal human, since very atypical non-verbal language makes them place you at the uncanny valley. If this seems like a lot of work to you, it actually is, which is why many autistic people choose not to mask.

If you need a step-by-step instruction on how to do that to mask properly, it'd just be best if you sought non-scripted Youtube videos where strangers talk to each other on the street (for instance, interviews). You will notice how "eye contact" isn't actually too constant, but rather gets broken and resumed all the time, especially by the person talking.