I eventually came to realize many of my spelling "errors" were actually due to my exposure to the British spellings for many common words I would see online, like color/colour or behavior/behaviour for example. Unfortunately my teachers were a little unreasonable about this and would still deduct points when I pointed this out...
To this day I still inconsistently use all spelling variants, and curse Noah Webster for his half assed attempt at regional spelling reform. In practice my phone just auto corrects them without me noticing though.