Ruby on Rails creator David Heinemeier Hansson on problem solving:
If you can get those magical 80% of the solution for 20% of the effort, how about just finding a way to cope with the missing 20% of the solution? If you can, you get to solve five easy problems (with comparable value) instead of solving one hard.
Oftentimes this is the right answer. In terms of software development, the question is whether the remaining 20% gives your project or company a strategic advantage over everybody else.