Opportunity Lost

I botched a Job Exam/Interview last monday.
I could make the excuse that I had less than 3 hours of sleep and my body ached all over and that I cannot concentrate with all the talking happening around me but the real reason is that I wanted to work there and that put pressure on me.
It was a programming exam and the problems were really simple, but being nervous made my mind blank for more than two hours. This was funny because the exam was for 2 hours and I spent about 3.5 hours on the exam.
Damn, I also realized that I have a problem with problem solving. The sheer number of ways that something can be done produces a paradox of choice state for me. I cannot start doing something because knowing the multitude of things , of ways something can be done starts my mind to doing seemingly intractable (at least using my very limited brain power) number of considerations.
This on quiet reflection has always been a problem for me, why I take a very long time to do seemingly simple/straightforward tasks, and why seemingly complex tasks require a minimum of time for me to do. The former because there are just too many ways to do it, the latter because of complexity reduces the possibilities to a point where I can make a decision.
I have to find a way to work around this. This has been holding me back for a very long time.