If you have received objective counsel from a wise person (counsellor or pastor trained in counselling) and have arrived at the point of knowing that you need to end the relationship, do so with sensitivity and Christian love – but with finality.
Trust God to provide for you and the other person in this situation.
Take a few minutes to think about what part you have played that contributes to the challenges in this relationship.
While you may not be a significant part of the challenge, it is more often than not that we contribute to some of the causes for the challenge(s).
Then consider how to approach this topic in a way that affirms the relationship but does clearly shares that it is a detriment to the end of a relationship.