Better practice makes better success.
End every training session with a/some penalty kick/goal. Make kicking a routine.
Work on the form, the physical, the mental.
Variation is key, different goalies, targets, surfaces, environments, distractions, balls,…
Work on your fake. Hide your weapon.
Get to know your opponents. Strong and weak points of the goalies.
Get absorbed by the task, love kicking a penalty (autotelic experience)