Rebalancing your portfolio every once in a while is important. But it is counter-intuitive and can be scary at times. However, opportunity and returns come from buying low (when times are scary). You would not want to do this with individual stocks because those can go to zero value. Mutual funds (ideally indexed funds) and a properly diversified portfolio are prerequisites.
More importantly … keep an eye on your goal when you feel your emotions take hold.
A prudent plan considers your emotions as well as present and possible future economies and markets. A structured approach means you may not need to make big changes just because the economy or markets changed.