Because we are working in such small increments, the only thing we need to come up with at a Retrospective is something to try out for the next few weeks: an experiment. Because we are only going to try the experiment for a limited amount of time, any negative impact is controlled by the fact that when we meet again we will decide not to do it anymore.
Source: Actionable Agile Tools, Jeff Campbell, http://leanpub.com/actionableagiletools