Yes that's right, you didn't lose your money or bitcoin unless you sell when the market is full of red. So when the market is full of red much better to buy more and hold it for you to gain your profit rather than sell. That's a basic part in trading ( i'm not an expert but that's my opinion )
Selling at loss is a decision no one should take unless it is a very small loss and you are sure of the chances of it going even lower. But once you have missed a loss of more than 30%, just hold on and find the perfect time to buy more and make a lot of profit from it.