Many times in a match, you will get bogged down on the little details. For example, you might be thinking, yesterday my service was a lot better, but now it's not working. Do not get bogged down on yourself or the details. It's about the "Big Picture." What can I do right now that will help me win this match? Quit worrying about things that are not working. For example, your first serve has left you. Quit forcing it. Just start the point with your second serve. You lost confidence in your backhand. Move around the backhands and hit your forehand and get the point started until your confidence returns.
In a doubles match, you are not returning serve very well. Ask your partner to move back to the baseline. That way your partner will not be "killed" by your "high returns." Try to make positive adjustments in your game. Do not think about yourself or the things you cannot do. Try to see the "Big Picture." Many times you're "A-game" will return if you do not panic. Until it does work, make positive adjustments and continue to get the point started.
In the "Big Picture" quit thinking about yourself so much. Ask, "What can I do now to make a positive improvement?" Maybe, figure out which player is weaker, which is stronger, who has the better strokes, who has the best volley? Use your practices and lessons to work on the details and your own personal weaknesses. In the matches, think about the "Big Picture."
Good luck on the courts!