That happened to me two years ago... Like Irene above, I knew my job was not doing well. We actually had THREE rounds of layoffs at my job and eventually got to the point where there was a handful of us left so we just started working from home. It continued for about a year and a half and the last few months I realized much less work was coming in. I don't even know how because I was the only person doing my specific job, but just nothing was coming in. I was seriously signing on and doing nothing for 7 hours. >_> Well, I can't say I was doing nothing because I'd just work on my comic when there was nothing to do.
I started looking casually for a new job and even had a phone interview where they told me "It's really difficult to find people with your experience!" So I thought it was going well and then... dead silence. I emailed them back and nothing.
And then I was let go in May and at that time... I had an entire vacation to Japan planned out. I had no idea what to do now that I had no job. Should I still go on it? Should I save up my money? Not only that but now I was having a lot of trouble finding a new job. Even with the new amount of experience I had, I had ZERO call backs in all of the resumes I sent out for jobs I was perfectly qualified for.
The good news was that one of my old managers who was let go during one of those rounds of lay offs had a new job at a place that was growing and hiring. So I had an idea that I would likely get a job there because he knew I would be a good fit. Because of that, I did end up still going on my vacation and don't regret it at all. And after I came back, I had an interview and was able to start my new job in August!
I don't know how it is for your job type, but for mine as a graphic artist you basically HAVE to know someone or have an absolutely amazing resume/portfolio. The thing is every boss out there knows someone whose son/daughter/niece/nephew/etc has just graduated and kinda knows Photoshop so they just hire them for $10/hour or whatever so the competition is very fierce.