Robert Burns was a shrewd observer of the human condition. He wrote that the best laid plans of men and (more surprisingly) mice often go awry.  If you understand why plans get blown off course, you can start building more resilient plans.
The good in-house lawyer plans. Not just project plans for executing an M&A transaction or a litigation case management. They plan about changing culture, transforming attitudes and realising opportunities. They may be setting up a new team or system or changing the way in which business people interact with the lawyers. It does not matter how hard people work at a plan, sometimes – indeed often – they fail to meet the majority of their objectives. Some even fail completely.
“Everyone has a plan until they get punched in the mouth” is Mike Tyson’s contribution to business planning. One reason a plan will fail is when it is operated in an inflexible way. The British Army teaches “It is the man in the plan not the plan that counts.” Plans should have flexibility and be capable of adaptation during implementation. Those who stick rigidly to a plan without adapting their tactics create the opportunity to fail.
Understanding the role of planning assumptions is important. Some self-help books tell you not to make assumptions, but in planning you must. You cannot know everything. As Donald Rumsfeld memorably explained “there are… unknown unknowns. There are things we don’t know we don’t know.” If you do not make assumptions you will never be able to start planning. Instead you will be worrying about what you will never know.
Some assumptions will be wrong. I guarantee that. Accept the premise and adapt to changes in circumstances. Once again, Donald Rumsfeld offers guidance. “It isn’t making mistakes that’s critical; it’s correcting them and getting on with the principal task.”
Managing those with a stake in the plan is vital. Agreeing a plan in an organisation makes getting a unanimous resolution in the UN Security Council look easy. Once agreed, you must invest considerable amounts of time marshaling the stakeholders and their interests to achieve the plan’s objectives. If you do not, individual stakeholders who were flaky in their support at the outset will end up running guerrilla tactics against the plan.
Timing is also important. When approving a plan, the approvers always believe that the timing is right. I have seen many good plans fail because the timing is wrong. In particular, planning in reaction to events is high risk. Politicians and others often say after a calamity that people must plan to make sure it never happens again. Such plans – whilst well-intentioned – are often poorly thought through as they are reacting to a past event, not future ones. Learn from mistakes, but remember history rarely repeats itself.
Having a plan is a good idea for all the right reasons (defining success, allocating resources, managing risks etc.). Plans fail because of poor execution, but also for the reasons I have listed. Thinking about those reasons and how you manage their consequences is time well spent.
Obiter Dicta: Burns and the Army both talk about plans and men. Do they imply women’s plans do not go awry? Is that something for men to consider?
 Do mice really plan?