Fail fast, fail cheap

One of the lessons fom the fast-moving technology sector for new businesses or new projects is "fail fast, fail cheap".

This does not mean that you start a business with the intention of failing, but that you must have pre-determined measures of success and failure. By observing these you control your costs, and the losses you suffer if you fail. This is one of the hardest things to do for a project you are passionate about.

The BBC expresses this as "Fall forward, fast: make many small bets, iterate wildly, back successes, kill failures, fast."

(from The BBC's Fifteen web principles)