Following a plan is a good guideline, but responding to change it critical
We work well if we know the end result that is needed. Having a project plan, helps us to organise our activities. The idea to have a plan is good and can be very usefull. It makes it difficult however, in responding when a change is needed. The need for responding to change is mostly unplanned. Changes are often not easy to understand.
The situation is further complicated, with increased project complexity. It is difficult to manage tasks, when they depend on each other for instance. Complexity increases further if we consider the people in a project. It is difficult for us to stop in the middle of a task. Let alone for us to change the task and start again.
Responding to a change, needs to be quick and with the least amount of effort. Agile relies on techniques such as INVEST. This technique allows us to express business needs easily. For instance a story should be small. Small stories allo us to respond to change, since we can quickly understand the need. The amount of work to implement the change is also limited, since it is small.
Further techniques assisting in a quick response, is for instance daily standups. Having short frequent meetings, allow checkpoints during a development cycle. This checkpoint allows you to share with others your progress and get support if needed. We can say what we did yesterday and will do today. In addition we can state problems and the team can help us resolve it.
Finally another technique is to have sprints, which are typically two weeks. Sprints allow the developers and product owner to sync often. Sprints are short cycles, which make responding easier for the team. Changes are often from the product owner, so early change requests are needed.