The phase you're looking for is tax loss harvesting. A good money manager on a good fund will be able to take advantage of that in a down market, leading you to

The phase you're looking for is tax loss harvesting. A good money manager on a good fund will be able to take advantage of that in a down market, leading you to greater riches when there's a bull market. You can do it yourself, but you can also pay a professional to do that work for you, hence the fees on a given fund.