Grit is the determination to succeed and may be as important as ability. Passion and commitment help overcome inevitable setbacks that occur in any long term undertaking.
Grit is a quality you demonstrate when you make the choice to show up for what you really want for yourself, no matter how difficult. Get clear what you want then walk through the fear.
Admit it is difficult to change long-standing habits, ways of being and thinking /mental habits, then make the commitment to accept the challenge.