I once sat in a meeting of project and business updates and suddenly one of the directors said, actually with all that we have now we can be in the medical device market. Violaaa!!! This medical device company used to service government hospitals and they have all the equipments. It's just that they never thought of going direct to the hospitals and take the lion share of the business. In that meeting, after going through the company yearly updates, this "innovation" came instantaneously and the next year they are pitching about it to the government hospitals directly.
Corrective Plan. A marketing plan is a living document. Trust me, the moment you have it and experience planning your marketing, you will realize this. Therefore it is a plan that allows you to assess past strategies and results and at the same time allow you to make necessary corrective measures to fit your business growth. for example, who expected the 2008 financial crisis to hit us so badly? No one other than the few so called "economists" but how did responded to it? Severely. Many businesses closed including many giants. But the good thing is, many have a solid marketing and business plans, therefore they make quick corrective actions and moved forward.