Getting fired is always a traumatic experience because it brings anxiety and uncertainty into your life. As with any major life-changing experience you will go through many different emotions, from disbelief to anger to depression. However, it can also be an opportunity for change and growth if you are willing to make the most of the opportunity. This sounds strange, especially given the state of the job market today, but it is true nonetheless.
Different companies deal with employee performance issues in different ways, and they have different steps in the process. Some will fire someone for one infraction. Others have several stages, going from warning to probation to termination. In most cases, unless the performance issue was an egregious one (such as theft), you will have advance warning that the termination is coming and will have been given time to improve your performance.
If this was the case, and if you've been fired, as opposed to being laid off, then you should consider the possibility that your poor performance was an indication that you were unhappy with the job in the first place. People can be laid off for reasons beyond their control, but firings are almost always the result of poor job performance. Poor job performance often results from a lack of satisfaction with the job you are doing.
Maybe you ended up in your last job because it was the best you could find in a sagging economy. Maybe your career path was originally chosen more to please your parents than yourself. Or perhaps you simply got comfortable in a situation that deep down you really didn't like. Any of these factors can cause you to not only dislike, but even resent the job you were doing. Being fired has opened doors you might have never gone through voluntarily.
Now is the time to figure out what it is you really want to do, an opportunity to find a career that will make you want to go to work in the morning. Before you start sending out resumes to every company in sight, take some time to really evaluate what you love to do, what you do well, and then what types of jobs fit both of those categories. Perhaps you need to go back to school for additional training in a field you really want to be in.
The best advice I ever received was "find something you love so much you'd do it for free, and then find a way to get people to pay you to do it." This may not be possible at first, but if you start moving your career in the direction of doing something you love, you can get there. In the end, getting fired could be the best thing that ever happened to you.