Wall Street just ended its best August in years, with the jumping more than 3 percent in its best August performance since 2014, while the Nasdaq had its best in 18 years.

It doesn't get much better than this, according to one strategist — and that may be the problem.

"The shorter-term data looks good, second-quarter revision to GDP looks good, earnings look great but if this is close to just 'it doesn't getting any better than this' we think it's the right time to buy low, sell high," Mark Eibel, director of client investment strategies at Russell Investments, told CNBC's "Futures Now" on Thursday.

The markets are engaging in a type of "battle royale" where good news faces off against the prospect of bad coming down the pipeline, says Eibel. Strong economic growth and record earnings have given the bulls energy, while expected higher interest rates and a steep momentum rally has given bears reason for pessimism.

"We know valuations are more expensive in the U.S., we know that interest rates are going to be moving up so you do have this daily battle going on," added Eibel.

The S&P 500 trades at a price-to-earnings ratio close to 17, with some of its components such as Netflix and Amazon at an elevated multiple more than five times that.

The other bearish argument, higher interest rates, is a given among market participants. Markets are pricing in the near-certainty of an increase to the fed funds rate at the Federal Reserve's September meeting and another in December, according to CME Group fed funds futures.

Earnings growth among S&P 500 companies should also top out at these levels, and limit further upside for stocks, the investor said.

"We all know that the comparables to a year ago were easier to beat, and you have tax reform that was included in this year's number and not last year's so there's no arguing that the earnings were good," he said. "Take yourself out another year from now: What do those earnings comparables look like?"

Corporate earnings have never been higher with record profits for the S&P 500 during the second quarter. Analysts surveyed by FactSet anticipate 22 percent earnings growth for the full year, though that pace will likely be cut in half in 2019.

"We just think it gets harder and harder from here in the U.S.," he added. Instead, Eibel is looking abroad for better opportunities.

"We like Europe, we like Japan. We like zero interest rates, cheaper stocks and economies that are doing well enough and earnings that are coming through. We just think it gets easier outside of the U.S. at this point in the U.S. cycle," he added.

Eibel and his firm are overweight Europe, slightly overweight Japan and market weight emerging markets.