"Defense is more important than offense" right now, said Marks, the author of "Mastering the Market Cycle: Getting the Odds on Your Side."
Investors should consider taking a stake in utilities, and decreasing their investments in more volatile tech stocks, he said.
Defense is the name of the game for a few reasons.
Though stocks have been soaring, Marks warned that we may be nearing the end of the bull cycle.
"I'm not saying get out," he said. "I think that being out of the market is pretty dangerous today, and I think it would be a mistake to raise cash." But more reliable stocks can protect investors from big losses if the climate changes.
Marks also pointed to the trade war with China as another reason for investors to tread carefully.
"We have a trade battle with China, it's probably going to get solved, but it may go off the rails," he said. "And if it goes off the rails, it has very serious consequences for the world economy."