I remember reading a research (don't have a link, sorry) that when one employee gave a one-week estimate and another employee gave a two-weeks estimate for the

I remember reading a research (don't have a link, sorry) that when one employee gave a one-week estimate and another employee gave a two-weeks estimate for the same task, and each of them delivered the output in two weeks, most managers perceived the first employee as more competent. Which, if true, would explain why most software projects are underestimated -- people instinctively perceive this, and want to be seen as competent. An interesting experience is to estimate things in your own life. You plan to do something, write down when you expect yourself to finish it. It is quite humiliating to notice the effort you put into convincing yourself that you are more productive than you actually are. Unlike with job, you can't make the excuse that impressing other people is a good strategy. Yet, it can take a lot of work to stop doing that.