Focus is not one long, unbroken beam of attention. Even elite athletes lose focus constantly. What separates them is how fast they notice they have drifted and how quickly they return to the one thing that matters right now.
Most focus problems are really attention-direction problems. Your mind gets stuck on things you cannot control (the ref, the score, a past mistake) instead of the controllable cue in front of you. Training focus means training that redirection until it becomes automatic.
You cannot force yourself to stop thinking. You can choose what to point your attention at, which crowds the distraction out.
The core skill: a reset cue
A reset is a small physical action tied to a single focus word that snaps you back to the present. Wipe your hand on your jersey and say "next." Tap your stick twice and say "here." The action interrupts the spiral, the word gives your attention somewhere to go.
The guides below build focus from three angles: holding it during play, resetting after mistakes, and locking it in before you even start.