The dot-com bust, the Great Recession, the housing collapse, stagnant wage growth — these are just a few of the many financial setbacks Generation Xers have faced during their formative adult years.

So, it's no wonder nearly two-thirds of Gen Xers stay up at night, worrying they won't have enough money in their retirement funds for their Golden Years. This is according to a new survey released by American Funds, a mutual fund family operated by Capital Group, which surveyed more than 1,200 American adults to discern generational differences in retirement and investment outlooks.

While Generation Xers, aged 37 to 51 years old, face similar financial challenges to Millennials, they have fewer years to catch up, which is why American Funds dubbed the group 'Generation AnXious.' They're the most pessimistic about retirement, compared to other generations, according to the survey.

"Perhaps because of these concerns, Gen Xers long to do better than the average market and say actively managed funds can help them reach these goals," said Heather Lord, head of strategy and innovation at Capital Group. Lord examines data on how people invest over time.

The survey also finds one in three Gen Xers say they don't earn enough to save for retirement.

To help catch-up, Lord suggests Gen Xers should consider working with financial advisors to identify funds with low fees and high manager ownership, which means the fund manager invests in his/her own fund. This, Lord says, is a proven characteristic of funds that outpace their benchmarks over time.

Although Gen Xers seem most anxious about retirement, it is Baby Boomers who are most bearish about market expectation. Over the next decade, only 16 percent of Boomers expect the market to do as well or better than the last five years. In contrast, nearly twice as many Millennials (31 percent) and Gen Xers (28 percent) picked the most bullish scenario.

"Every generation is interested in achieving better investment outcomes over time and limiting losses in market downturns, combined with low fees," Lord said. "But each generation has blindspots around index funds, which experience the full downside of market drops. Baby Boomers, especially, are unaware of those risks – and they're the ones with less time to rebuild their nest eggs from a market downturn."