Rebalancing
Trading back to your target mix.
Rebalancing means adjusting your investments back to your chosen mix after market moves have pushed it off target.
How it works
If your plan is 80% stocks and 20% bonds and a strong year pushes stocks to 88%, you sell some stocks or direct new money into bonds until you are back at 80/20.
With regular contributions, the easiest way is to point new buys at whatever is underweight, which avoids selling and possible taxes.