Why did the United Kingdom leave the European Union and was it a good or bad decision?

The UK voters that favored an exit were mostly motivated by two fears: 1) the fear that the UK was being overrun, firstly by east European workers pushing British workers out of their jobs and taking over the work; and secondly, by Third World refugees without any useful qualifications who would only become an unemployed underclass and a huge drain on the British social security system. And 2) they felt that the EU was continually working at creating a supra-national State, making ever more rules and regulations and taking power away from individual nations that so were losing all say over their own destiny.

The British moreover and understandably have somewhat of an 'island mentality' that makes them cherish very much their "Britishness' and makes them wary of foreign influx and meddling.

How this decision will work out is uncertain. The politicians and economists in favor of an exit have argued that this newfound freedom will be good for its financial services industry, that it will give the UK new commercial opportunities and that is will keep British society together and the social system sustainable. Politicians and economists that are pro-EU argue that this will mean the end of London as a financial center and that Britain's prospects of economic growth will decline. Only time will tell how this exit will work out, however.