Sentence:  Designing a window without the building, a light without the room, or a motor without the machine it drives works as badly as designing a pelican without the fish. "Optimizing components in isolation tends to <WSD>pessimize</WSD> the whole system – and hence the bottom line." 
Meaning of the word marked with <WSD> tags:  To make (something) pessimal or the worst;  to make (something, such as a computer program) less efficient.