According to a University of Michigan Ann Arbor study, the physical act of washing your hands can help remove those niggling second thoughts about a decision you've made.
Photo by Arlington County.
The metaphor of washing your hands of something as washing your conscience (or your mind) clean may have some basis in truth. Graduate student Spike W.S. Lee conducted the study, analysing how individuals reacted to decisions they made based on the simple act of hand washing. Lee found that when people literally washed their hands after a decision, they felt justified about their choices and felt increasingly better about their decisions. When people did not wash their hands, they were less likely to justify their decision.
For more interesting tidbits on the relationship between hand-washing and its effect on the mind, the NPR podcast (embedded above) also offers more food for thought.