First of all, yes, I have been fired, more than once. When I finished my MBA, some smart professor told the whole class that indeed, each of us WOULD be fired at least once in our careers, and if we weren't, we probably weren't all that effective. A controversial stand, perhaps, but so true for me.
The times I have been fired have been due to company lay-offs (but who lands on the layoff list is almost always partially political), or in one case, a start-up that failed. But still, regardless of the circumstances, for us over-achievers, when it happens to you for the first time, it is an ego blow for sure.
I have found that the experience of getting fired has made me pretty fearless professionally. I do what I know is right, regardless of the risk of getting fired. Feels pretty good integrity-wise.
Of course, it's easier for me to say that because I am financially able to withstand a few months with no paycheck.
I'd encourage everyone to work toward having a financial plan or cushion, if they DO end up going without a gig for a little while. It's a horrible feeling to have to do something you know is wrong for you, or to stay in a bad job, because you can't afford NOT to.