With concerns over emerging markets keeping many investors up at night, shares of the bank that "never sleeps" have taken a beating. Investors shouldn't toss and turn too much, though.

Citigroup has fallen nearly 8% this year, while JP Morgan Chase is down less than 4%. Highlighting the division between banks with an international bent and those more exposed to the US economy and housing, Wells Fargo is off about 2% and Bank of America is up more than 6%.