This. Its so important for workers to realize just what predicament they're in. So while it was possible for lifelong jobs to be possible in the past, its not so much the case today. No job is really secure, and one does have to stay on ones toes.
Not saying that you should be concerned about getting fired everyday. But if you don't create demonstrable value to your company over a longer period of time (a couple of years perhaps) don't expect to keep the job. Things are moving wayy too fast today.
Generating value is only a small part of it. You can get fired or laid off for any reason in most places in the US. You can be doing great work personally, but if upper management screws up, or the business environment is just bad (despite management's best efforts), you'll get laid off as soon as it makes financial sense for the company to do so. You can also get canned or at least mistreated to the point of misery because of interpersonal problems having nothing to do with your performance, a terrible manager, etc.
Not saying that you should be concerned about getting fired everyday. But if you don't create demonstrable value to your company over a longer period of time (a couple of years perhaps) don't expect to keep the job. Things are moving wayy too fast today.