In stock trading, we learn to cut losses when the price isn't going in our direction. When a loss isn't cut fast enough, a small loss can quickly turn into a bigger loss. You might hold and hope that things magically work out in your favor, which it almost never does. Your capital is tied up while it could be better invested elsewhere. 

In order to achieve that, we must change our reaction and in that case, it would be the fear of losing. You repeat and practice so many times that you accept losing subconsciously. You need to cut your losers and train your mind to have a long-term mindset in order to win. I think that applies in all areas of life.