These are not the same thing. Suppose it's deuce in the fifth, and you make two awkward, weak returns that hit the edge. You've won!!! You are so happy. But the shots you did were not good. You should be happy about the outcome, but unhappy with the process.
Now supposed at deuce in the fifth you pull off two very nice shots, but your opponent makes a pair of weak returns that hit the edge. You've lost!!! You are so sad. But the shots you did were good. You should be unhappy about the outcome, but happy with the process.
If you focus on the process - i.e. your actual shots - then you'll maximize your chances of getting a good outcome. So, learn to separate outcome and process. When you lose, it's fine to be unhappy with the outcome, but you'll learn more if you examine the process, see what you can learn from that, and focus on improving your process, i.e. your game. And that will lead to better and better outcomes.