Repetition is key.
Every day, do something to improve yourself. And repeat it. Every. Day.
Trying to learn to play an instrument? Practice every day. Repeat the habit until it feels unnatural to not play.
Want to learn a language? Speak it. Every. Day.
Repetition breeds learning. It breeds behavior.
Nothing that is truly worth doing can be done only once and complete the change we seek in ourselves. It must be fought for. Repeatedly.