The funny thing about planning is that it must be done, but it will almost always have to be re-done.  Nothing ever seems to go quite as planned, and no matter what great lengths you go to in order to have all possible scenarios accounted for, something is always guaranteed to surprise you.  But it’s not the surprises and challenges that cause projects to fail – it’s the lack of adaptation to them.

I have often told people that any project that goes exactly according to plan is probably too small and simple to need much of a plan in the first place, and is almost certainly too simple to need a dedicated project manager*.

The real value of a project manager is seen not when things are clipping along smoothly, but when there are challenges to overcome.  When things don’t go according to schedule, you must be able to adapt the schedule, adjust your plan and get creative.  Some of this can be done in advance, in the form of contingency planning, but that only works for risks and hurdles that you can anticipate.  The proverbial "unknown unknowns" are where the real test of adaptation comes.

A big component of adaptation is managing peoples’ expectations, which brings us back to communication.  When things aren’t going according to plan, instead ignoring or covering up the facts, you should be communicating with people (both team members and stakeholders) early and often about the challenges you face.  Most reasonable people will appreciate the honesty and do what they can to help you adapt.

Remember that the goal of the project is to solve some problem, deliver some product, or achieve some particular outcome.  It is not to follow a plan to the letter.  Adaptation is usually necessary to meet your end goal.

*please note that I'm not referring to standardized, repeatable projects where a plan is created once and executed many times.  Hopefully, with those types of projects, you do get to a point that it all goes according to plan a majority of the time.