I always try to know more and more about future of all coins related to that trade ..and if I lose i try to make another profit to cover my losses .Trading and investing focuses more in gaining profit through taling advantage of market's flow.
there is nothing special to do with the loss you just have to be confident on your investment if you have invested for longer term because loss is the part of the game and you don't have nothing to do with it. i think in order to deal with it you have to just analyse the coin in which you are investing by analysing its previous chart and performance and then invest in it.