I will go with December being the worst month of the year to trade forex because portfolio managers, banks, investors etc. are wrapping up and tidying their books so the market could be excessively eratic.
Been trading forex for a few years now and I noticed January is a terrible month to trade because the markets are just recovering from the xmas break and most institutional traders are still on holiday. This causes liquidity to be poor and price action behaves inconsistently from what you have been used to.