1. Read "Winning the Mental Match" by Dr. Allen Fox - read this and it is a great book
2. Read "Winning Ugly" by Brad Gilbert - only read excerpts from this one and will buy it as soon as it is available as an e-book - good excerpts and good feedback from others
3. Recognize that complaining that my partner is not good enough for me to win is a cop-out. Inconsistency is your shots may reflect technical and mental weaknesses in your game. Are you hitting enough spin on your 2nd serves to be consistent under pressure? Do you hit enough topspin when returning weak 2nd serves to hit the return hard and keep it in the court? Can you keep intense mental focus during a match but still keep muscles/body relaxed and swing free of tension?
Good luck and exposure to match conditions will help a great deal.