Building a portfolio to meet your goals is just half the job done. You also have to monitor and adjust it to keep it aligned to your needs. This is because a portfolio typically holds assets that earn different rates of return. Over time the relative percentage of the assets will change, skewing the portfolio in favour of the asset class that earns a higher return. The altered portfolio may then have a different level of risk. Rebalancing helps restore the original allocation.
Monitoring and rebalancing your portfolio is a continuous maintenance plan. You may need to adjust your current asset allocation as the terms to your goals change, or if your needs and goals themselves have become different, or if your ability to take risk is not the same anymore.
