I have spent most of my career working in the public sector. Working in the public sector affects how you think. One quite common belief, as a public sector employee, is that you can never be laid off. And for most public sector/civil servant employees that will be true. However, I have been laid off twice from public sector jobs. I've come to believe there's no such thing as any job that is 100% safe from layoffs.
Steve and Kendra's admonition to consider what you might have to do, if the "bad day" comes, is excellent. Looking back at my last layoff, there were some hard lessons I learned from that. At the time I was working for a university. Working for a university meant that they understood the need for continuous learning. I took advantage of that, but I still failed to be properly prepared. For example, I had heard of unit testing, but we didn't practice unit testing in my group. (I'm a software engineer as was my colleague at the time.) Unit testing isn't one of those skills commonly listed, even 8 years ago when I was laid off. But it is one of those basic skills that is expected you would know. I found a free video tutorial on unit testing online. I watched it and practiced it. It helped me get re-employed.
So, in conclusion, make sure that you know the basics of your trade. Those basics probably won't show up in job post listings, but when you're in an interview and it becomes evident that you don't know some of the basics, you're through.