Volatility could certainly return for the end of 2018. 

The trade spat between the U.S.' Trump and China's Xi Jinping is still ongoing, leaving investors uncertain, and leaving the market vulnerable to jolts in both directions

JJ Kinahan, Chief Market Strategist for TD Ameritrade, broke down what the common mistakes investors make in the midst of uncertain market conditions, and what some good solutions are. 

Kinahan laid out one core investing principal. "Know your time frame," he said. If an investor has a longer time frame, short-term volatility doesn't have to be so scary. He added, "I see it too often where people buy something -- they say 'I'm holding it for a year,' and then after a move {price move} in a week they're like 'I've got to get out.'" Hold strong, is Kinahan's message. 

His second lesson is to buy shares in small bites if uncertain about how they'll perform. "Trade smaller than you'd think," he said. "Use movement {price movement} as your friend, not your enemy." 

He gave an example. If an investor has the capital to buy 500 shares of a company, but he or she is uneasy about the stock, maybe it's better to buy 200 shares at first. Then, if the stock does come down and it's a buying opportunity, the other 300 shares can be bought at potentially a discount, and gains on those can offset losses on the first 200 shares. "If you buy all 500 at one price and we go down, too often people are like 'oh my god, I've got to get out, and they put themselves in a bad situation," Kinahan said.