The single most common cause of both work overload and project failure is doing work twice. The most common cause of that is picking up some piece of work (opening an e-mail, looking at a piece of code, whatever), and not handling it right then and there, but instead deciding to handle it later. Right there, you just made yourself do at least twice the work of analyzing whatever it is you just had to analyze a first time. The second most common cause of double-work is not doing something right the first time, usually in a false sense of "just get it done".