in psychology is a positive, non-cognitive trait, based on an individual’s passion for a particular long-term goal or end state coupled with a powerful motivation to achieve their respective objective. (wikipedia)
Those who succeed most likely have a strong motivation to persevere the goal and achieve, with a strong resilience in face of adversity.
Grit involves maintaining goal focused effort for extended periods of time, often while facing adversity but does not require a critical incident. Importantly, Grit is conceptualized as a trait while resilience is a dynamic process. (wikipedia)