DRY (Don’t Repeat Yourself)

I’ll say it again, don’t repeat yourself. 

“Aimed at reducing repetition of information of all kinds, the DRY principle is stated as "Every piece of knowledge must have a single, unambiguous, authoritative representation within a system."” 
- http://en.wikipedia.org/wiki/Don%27t_repeat_yourself 

“The Don't Repeat Yourself (DRY) principle states that duplication in logic should be eliminated via abstraction; duplication in process should be eliminated via automation.  … Duplicate code adds to technical debt.” 
- http://deviq.com/most-popular-principles/don-t-repeat-yourself 

In other words, don’t wear out your V key.

As with most of life, however, DRY shouldn’t be taken to extreme.

Practice thoughtful moderation.