Integrity is choosing your thoughts and actions based on values rather than personal gain. You need integrity to STAY in God. Because whatever you do for your personal gain will KEEP you in pride not in CHRIST.
Frankly, this does not sound like a JFK quote. This doesn't even feel like a JFK quote. Perhaps someone has taken Internet liberty and license to attribute this to him. "One person can make a difference, and everyone should try." John F.