Last night I ran into a problem that took way longer to solve than I expected.
The delay had two causes: I was working from an incorrect assumption, and I
couldn't test each case of the solution space generated by my bad assumption.
Because I was uncertain of how much of the solution space I had searched, I
undoubtedly reduplicated efforts, which added delay. When I guessed I had
searched enough, I examined my assumptions and found the error.
All this added up to a big bunch of inefficiency.
Clearly, I need to work on my problem solving skills. In the future:

- Define solution space
- Test each case in order of decreasing probability
- At some probability level, examine assumptions.

The probability level should be determined by cost to evaluate remaining cases
versus cost to check assumptions. Both will be estimated costs; good luck. ;)