Their backup plan? Work.

More than a third—36 percent—said that if they fail to accumulate enough assets to see them through, either they or their spouse would work longer and/or join the gig economy.

Still, 86 percent said that their investment goals are focused on long-term returns like retirement income or leaving an inheritance.

And those confident millennials? A surprising 60 percent (compared with 29 percent of respondents overall) confessed to making an emotional decision to sell in a 401(k) plan that they later regretted.

Emotions ruled other demographics, too, to varying degrees, with 34 percent of men compared with just 21 percent of women admitting the same.

Kids may have driven parents to make emotional decisions, too, since 54 percent of investors with kids in the household pled guilty, compared with just 13 percent of those without kids.

More money wasn't proof against emotions, either, with 41 percent of investors with annual income of $100,000 and over owning up to regretting an emotional retirement plan decision, while just 21 percent of investors with annual income under $100,000 'fessed up to a similar offense.

And 47 percent of investors who self-identify their investment knowledge as “expert/advanced” apparently don't know as much as they think they do, since they likewise confessed to being ruled by emotion, compared with just 11 percent of those who classified themselves as “beginner/rudimentary.”

But there's plenty of room for improvement, especially since 22 percent of employed investors—including 34 percent of boomers, but only 11 percent of millennials—own up to not actually knowing the details of their 401(k) allocations.

Not that their allocations—when they know them—are all that great, since boomers are carrying 60 percent equities in their accounts, when it might be time to start guarding against market volatility.