Learning from losses is more valuable than learning from successes. Because when you succeed you get blinded and think its going to continue. Another thing is that it puts you in the mindset that your untouchable. Then you get comfortable and you crumble when something does not go how it should.
Well if you take time to learn from those whom have lost lets say a pitch for a client or had a failed startup you would learn more from them than someone who has succeed. Because you will learn what not to do. Also you will learn what you could avoid doing. Losses are a time when you can either fall or stand up and learn from them.
Currently interviewing in the process of securing a full time Graphic design position and I will admit before when I would interview I would think I did not have what it takes. But you know what I learned that I do have what it takes. All of the time before I would get the copy and pasted email saying they had chosen another candidate. You have the confidence in yourself to learn from those rejections and to not curl up in your bed and pout.
Nothing is learned overnight and especially your losses will seem to be constant. You may even hit a point where you think is anything going to go my way? When you hit that point keep going and remember that thinking positive is good. But its more than just thinking positive. You will need to take action while thinking positive. Also keep a diary and set weekly goals to be in the correct mindset.