MISTAKES THAT WIN: You can learn from your mistakes if you can see them and admit that it was you who made the mistake. Do not blame the President, the Mayor or your partner; take responsibility, own up to your error. Remember, playing Bridge does not involve being right or wrong. Save that for church or the court room. If, however, your partner makes a mistake that is another story. He is a brain dead jerk who should rot in hell. 
        To win at losing, use the information learned from your mistake; observe and correct. Do not be discouraged if you make the same mistake more than once. Playing Bridge is a process; not something that is goal or result oriented. (Try telling that to your partner after you made the same mistake four time in a row. He might cut your whipping time in half.) 
        Do not  feel guilty about making a mistake. If you clearly see your error and own that it is yours, then you will improve as a player. Guilt, remorse, recrimination by your partner or yourself will only get in the way of observing and correcting the error. It is sometimes helpful to calmly and objectively discuss a particular hand. This should usually be done after the game or match so as not to annoy your opponents - unless of course you want to.
        You will not win every game that you play. Unless you are playing in Bridge heaven where you always make the perfect bid; make every hand; and set all the opponent's contracts. This could get terribly boring, so you might want to play in the other  place. Losses are part of Bridge life; so accept them. To win, you have to learn to lose. 
        Mistakes are often a symptom of not being at the table, not concentrating, not observing. They are a wake up call for you to wake up. Take a deep breath, walk around the room or wash your face with cold water. Get back to the table, to the present, the now.  And play one hand at a time.