I read somewhere, but have forgotten where, that having doing things same way twice is ok, only when you're second time repeating yourself, think about using an abstraction.

Or to say it more succintly, duplication is not a problem, triplication is ;)

I have found that following this simple rule I allow the development to go forward, and can go back to it when I have better knowledge of the system at large. At later date I might have a better luck in choosing the correct abstraction.