I have seen players with more talent and better strokes lose to players with less talent and even worse stroke mechanics. If a player with inferior strokes but a superior mental attitude beats you, that player has a huge weapon and is, in reality, the better player. The defining edge for the less talented player is mental toughness. Yet the player who lost tends to think he was the better player because his opponent had no weapons.
But mental toughness IS a weapon and should be part of your arsenal along with the backhand, forehand, serve, etc. You should learn to think of mental toughness as an integral part of your game. Don't leave home without it! If you have poor mental skills you should practice these skills just like you would a forehand or backhand. It is imperative that you understand that learning mental toughness is just like learning a stroke... you practice.
Let me explain how you practice mental toughness. You practice making mental decisions to forget your mistakes and move on. You practice not letting your losses get you down. You practice not letting your emotions control the show when the game is not going your way. You practice hanging in there when you are behind. You practice focusing on "the next shot is more important then the last mistake." You practice a relaxed mental attitude and learn to concentrate on the present, not the past or the future. You practice controlling your emotions and learn not to be angry, anxious or anguished. You practice, learn, practice, learn, practice, learn, practice, learn, practice, learn and bingo! Mental toughness becomes a habit.
Mental skills are far too underrated and the technical skills are far too overrated. I hear lots of talk about mental toughness, but very few players practice making daily decisions to develop these skills. Far too often a player wants a mental technique that will make his mind magically become mentally tougher.
Remember, many decisions, one habit and the mental toughness weapon is yours.