To work really well, it also helps to understand level N+1 or N-2, respectively--either by implementing a higher level abstraction in a lower level environment, or by working on two levels at once (and thus needing to understand the level below the lower level).

For instance, you might be stuck with using C or Java and thus have to reinvent higher level abstractions through clever use of function pointers or design patterns or something--hence thinking at N+1, implementing at N, and being mindful of N-1 as you implement. Or you may be writing in Python but optimizing code bottlenecks in C, hence when writing Python (N) you have to understand the C (N-1), and when writing C (N-1) you have to understand the assembly (N-2).