it depends on what sort of behaviour but i would personally try and do an action (a good one) that eventually becomes habitual and i would try and keep at it until i have changed that behaviour.
Believe me you have to keep at it because its easier said than done.
Also another thing to add would be to keep a cheshbon of how its going. you know, write it down, assess it and if today wasn’t so great there is always tomorrow to try again.
stay positive and dont give up..