This is trading within a day. Day trading doesn't leave any trades open for the next day. There are a few reasons for this: firstly brokers take commission for deals transferred to the next day, secondly not closing a deal when asleep leaves it unchecked and uncontrolled. Thirdly, it's quite often the case that the tool you are trading may have one price at the end of the trading session and a very different price at the beginning of the next, it is not always predictable. In addition, unexpectedly released news can dramatically expand the price chart. Further information abour day trading can be found in the book “Intraday trading: secrets of mastership” by V. Tarp and B. June.