Your options are hold the investment, sell, or buy more. I think your decision should hinge on your long-term expectations for the sector and VDE as an investment. A 30% price change in a few months is relatively normal in equities markets: if that kind of volatility makes you nervous to sell, investing in stocks might cause you some sleepless nights. On one hand, you've bought-in at a low point in the energy market. If you don't need the money, hold the investment and reinvest your 3% dividend for 5+ years. You could even buy more VDE -- a declining price is a value investor's friend. I expect you'd see a positive return on your investment if you're patient. On the other hand, if you need the money, or you think there's a better investment you can make with that money, sell VDE and buy something else. Tax-loss harvesting should be something you consider as part of a broader investment plan, rather than an escape hatch to get out of an investment on which you've gone cold.
