Though ethereum maybe down now and I see it as an opportunity to buy more coin because this fall is only temporary and will rise up again. If you decide to sell now, you will sell at low price and you may end up not making profit but if you keep that and buy more, you increase your chances of making more profit.
If ETH drops below $ 500 this is a good price to buy, but if over $ 500 you buy on you will lose. In the future I think ETH price will not be able to rise above $ 1000. This is for sure, do not expect too high on the Crypto market.