I began my first business - more than ten years ago now - because I was sacked. I was sacked partly because I didn't know the rules of small companies (having just moved from a large corporate) and partly because the person who wanted my job - and for a time, got it - was a brown-noser par excellence and pretty unpleasant with it.
I don't feel at all defensive or embarrassed about being kicked out. What I do feel a little ashamed of is that the truth is that without that, I may not have had the guts or will to begin my own business. I used to think how wonderful it would be, but I could never summon the courage. Only when all seemed lost (it wasn't of course, but it seemed that way for a couple of days) and I realised that in fact I had a lot of the basis of a business already in place - then finally I took the jump.
Whatever the reason, being sacked is traumatic and can leave you feeling vulnerable and lacking in confidence. Nowadays, even if you know the rules, do not have a colleague shoving knives in your back and no matter how well you are doing the job - you may be fired. Things - let's face it - are not looking so good now, particularly in the more recession-sensitive fields.
If the worst does happen, put the situation to the good and consider the possibilities of beginning your own business. USE the trauma to shift yourself outside your normal comfort zones.
Okay, for some reading this it will just not be practical - perhaps you need a secure income, in which case a new business in a precarious climate is not such a great move. But if you have flexibility, maybe a bit of redundancy package or some existing clients or some established reputation in a creative area, now may be the time.