Take every chance of fall to buy more instead of selling because once the price recovers, it will give good profit. It is for long term investment so wait for long and do not think for instant profit. Take this opportunity to buy and buy even ethereum because they have good value when return in good price.
There is no doubt the bitcoin price will recover very soon because it is expanding at the moment in the business world in a high rate as a digital currency and soon its price will rise to the previous level or more so better to buy now without thinking twice and like you have mentioned ethereum price too is low and doing ethereum investments too will be very profitable in the future but for any now is the time to buy and hold