Losses are painful, however they are part of the business, The Trading Business. In trading as in any other business in the world you gonna have losses, even the biggest corporations in the globe which hire the most brilliant minds to run their business, have losses. So the goal is try to minimize them, that keep you adrenalized all over the trading day.
Boredom is a big enemy of trading , it can play games in your mind.
Personally i believe that the worst about trading is to turn a winning trading day into a loser one because of any silly mistake at the end of your working day.