This isn't about Sport Psychology. Nor is it really a mental skill. This is truly a way to conceptualize your own free will and take hold of the choices and actions you live by.
Think about a chessboard. There are 64 squares on the board. Think about these squares as the objective facts of your life: where you live, how old you are, how tall you are, that you live in a world with other people in it, that the moon exists (shout to Ali G). Sure, we can argue about what is objective and what is subjective, because much of what we assume to be true is constructed in our mind, but this isn't that deep dive.
Let's assume those basics. Those are the squares on the chessboard that is your life.
Now, put the pieces on the board. The pieces of a chess game are the subjective opinions you hold and your created realities: I'm good at X, I'm not good at Y, I work here because it pays me a good salary, I don't do that because it's not possible for me to do so. Each piece has a different value, and each piece is not set in stone.
So, who is playing chess? You are. You hover above the chessboard and move the pieces around the squares of your life. In knowing this, you understand that you have agency. You have free will. You have the ability to impact the way the pieces move, and even the ability to change some of the squares.
For example, you work where you work but you don't have to work there. You can choose to change jobs. It might be challenging, and certainly there are many factors to consider, but that is a potential "move" you can make on your chessboard.
You don't play the piano, but you could learn. You aren't a distance runner today, but you can decide to begin being one tomorrow and then run every day for the rest of your life, if you should so choose. Too often we get boxed into an existing or comfortable idea of what our lives are and don't take the opportunity to think about what our best moves might be - or several moves ahead - and impact change to spawn growth and development in our personhood.
This also helps us conceptualize our thoughts. Our thoughts - which experts estimate we have between 50,000 - 80,000 of each day - are important pieces on our chessboard. They aren't necessarily pawns, but we often treat them like Queens and Kings. If we can recognize that we are able to move our thoughts as we desire, that we are not controlled by them but that we can control them, we can more positively impact the feedback loop between thoughts, emotions and behaviors. We can look at a single thought as a single move of a pawn from one square to the next and - to extrapolate the metaphor - we can keep our hand on the piece before letting go and decide to make a different move. To have a different thought.
How does this relate to your performance? Well, some days you may have the thought that you're too tired or unmotivated to train. Check that piece. Is that your best move? Other days you may be lacking confidence because of a tough opponent ahead. That the opponent is "tough" and you are not is a subjective understanding; a bishop that can be moved to another square. If you choose, you can see that scenario differently and gather confidence. Perhaps you feel trapped by your role on a team, with nothing you can do. That is a tower hiding in the background. Go speak to your coach in a calm, courteous manner and ask what you can do to impact your playing time or position with the group.
you are driving the bus for your life, not anyone else
Remember, you are not sitting idly by while life happens to you. You are in control of what you do when you wake up each day, and you can impact it by perceiving your chess pieces anew. You are the grandmaster of the game of chess that is your life!