What terrifies me about being fired is:
* I have a family to support, and even though we're well off enough to have a 6-12 month cushion, I've seen job markets where it takes longer than that you get hired
* The number of unprofessional or biased hiring managers is vastly greater than the number of professional ones (I was disqualified for a sysadmin position based on a background check showing a city ordinance violation from tenants I had who left garbage on the front lawn when I attempted to be a landlord in my early 20s in a small Illinois farming community)
* Just like in personal romantic relationships, you can do everything right and still get fired