This is used to describe people who exclusively use Sitka branded gear, and think they are better than everyone else because of it. Sitka's motto, "sick for it" is a common hashtag people use on social media when posting about Sitka gear, hence the disease "Sick-for-it-itis" . People that suffer from this disease are usually cocky, and look down upon others because they spend thousands of dollars on mediocre, at best, gear.

when you've done something so cringe you can't stop replaying it in your head and it stops you from getting on with your every day life