I have been fired by companies for very dumb reasons.
Maybe they spent some time thinking about it, but I never received any warning. Nobody ever said "We are thinking about letting you go because of these reasons, but we want to be fair so we are giving you notice so you have time to find another job"

Funny how companies always expect at least 2 weeks notice if I decide to leave.

I was canned from my first job after 4.5 years just because the company suddenly didn't have much consulting projects and they had no project to put me on, so I was just out. Oh, they came up with an excuse, I but knew.

I was at a local supplement company a few years ago that had great benefits and many long time employees (20+ years) A new CEO came in and did away with many of the benefits (great prices on their products for life), and canned many of the long time employees. No warning. No reason. They just decided to get rid of a large portion of the workforce. One person from every team had to go. One of my team quit on his own, but I was still out. My team all pleaded with upper management to keep me on. The answer was no.

I was once fired because I had too many stock options and the new owners wanted to replace everyone who had options, which they did. Of course they made up other bogus reasons, but a few insiders spilled the beans. And in less than a year, all employees had been replaced. I had no warning. I just showed up one day and was told to pack up and get out.

I was once fired because the boss didn't like me. Never did. I don't even know why he hired me. I knew from day one. I think my religion had something to do with it. When I was let go, he was out of the office and made his wife do it. He was nice to my face, but constantly badmouthing me behind my back to other employees, who told me what was up.

I was just suddenly let go from a contract position because the new manager didnt' want contractors. He started one day and never spoke to me at all, and had me out of there within 3 days. No joke.

In each case, I moved on and found better situations. I am good at what I do, but nobody is immune from being fired.

Whenever I get fired, I just feel like the company set me free and can no longer do anything to me. I got what I wanted out of them ($$$) and I move on. I'm good with it. It's the way things are, which is why I never feel one bit sorry if I decide to leave a company.

I am just realistic and know that no job is ever safe. My first job was fantastic for 3 years and then suddenly the market changed and suddenly it wasn't such a good job. Everything they promised would never happen, happened.
I know that no matter how good and valued I am at a job, if I leave, I will be missed for about a day or two. Even if they suffer trying to get the work done that I used to do, it doesn't matter. Once you leave a company, you are forgotten very soon.

I recently had a great manager leave the company. I seriously thought we would be in trouble because he did so much. Nope. He left. Other people took over. The company moved on and he is now largely forgotten.

To quote a great movie: "You are an asset. An expendable asset! I used you to get the job done."