It’s OK do deviate from the plan. The plan is only a guideline, not a strict roadmap which must be followed.

Usually the organisation ends up changing its direction somewhat as it proceeds through the coming years. Changes in the plan usually result from changes in the organisation’s external environment and/or client needs result in different organisational goals, changes in the availability of resources to carry out the original plan, etc.

The most important aspect of deviating from the plan is knowing why you’re deviating from the plan, i.e., having a solid understanding of what’s going on and why.