As the market enters September, investors brace for what is historically the most difficult month of the year for equities. With a legacy of poor performance and heightened volatility, September often disrupts the market’s momentum, raising concerns that this year may be no different. Adam Turnquist, chief technical strategist for LPL Financial, notes that “seasonal weakness in September could spoil the momentum” built earlier in the year. Since 1950, the S&P 500 index, as tracked by the SPDR S&P 500 ETF Trust (NYSE:SPY), has generated an average return of -0.7% in September, finishing higher …