“So how long,” he asks, “do you think you’ll take to complete the project?”
“Two weeks,” I say.
Three weeks later, I’m still two weeks away from completion. What happened?
It’s not like this hasn’t happened before. It’s happened many times before.
Rolf Dobelli says it beautifully in his excellent book The Art of Thinking Clearly:
[W]hy are we not natural-born planners? The first reason: wishful thinking. We want to be successful and achieve everything we take on. Second, we focus too much on the project and overlook outside influences. Unexpected events too often scupper our plans.
The second point is particularly pertinent in my line of work. I have a pretty decent idea of how long a project will take, if all goes well and if I could dedicate 100% of my time to the project.
What I tend to forget is that life often gets in the way. There are plenty of interruptions. Other “important”, “even more urgent” projects pop-up; ad hoc requests that are quick to resolve but that just as quickly add up to significant amounts of time; regular routine work that’s not quite factored in, because they are normally quickly executed, but every once in a while require a long, dragged-out bout of firefighting.
Dobelli has a solution for better planning. He suggests
[shifting] your focus from internal things, such as your own project, to external factors, like similar projects. Look at the base rate and consult the past. If other ventures of the same type lasted three years and devoured $5 million, they will probably apply to your project, too — no matter how carefully you plan.
Which is a great case for keeping a log of project and their time to completion (do NOT trust undocumented recollections of project lengths; like childbirth, our brains tend to underestimate the amount of time and pain we go through).
Also, one more thing I would is that you resist the temptation to think that “this time is different”, and that no matter how confident you are, this time is probably not.
Trust the data.