Frustration

I've been thinking about frustration because it's a serious issue, likely to go from simmering resentment to full-on rage in a very short space of time.
My personal frustration stems from the situation in which I find myself with regard to the ever-widening gap between my dreams of being an author and the reality of my day job. I wish to write, but until I am successful I have to keep earning money. In order to do this, I have to continue working in a job with which I am not all that enamoured, despite what I might sometimes say.
There are benefits to the job, of course, but there are also serious drawbacks. Chief amongst these is my mental state after a day in the office. Spending 8 hours in front of a computer having to be moderately intelligent leads to a serious deficiency in imaginative and literary power come the eveningtime. Whilst I am often afforded the time in which to write, I typically lack the willpower or creative talent with which to do so (okay, so the talent bit is missing all the time, but I like to fool myself that this is the result of my job).
This, of course, is a bit of a problem, since I need to be able to write in order to quit the job, and in order to write I need to not be working on anything else. This is my personal definition of frustration. What's yours?