A relationship with the wrong person can drag you down, particularly if your friend has a strong personality and begins to put pressure on you. I think many people who have walked with God have built unwise relationships, and little by little, over a period of time, their convictions have been whittled away. Their desires to please God have deteriorated and they have been dragged away from their moorings. After a while, the fellowship and the friendship loses its spark, loses its real strength. Before long, the fellowship and the relationship is broken apart and someone is badly hurt.
Unwise relationships can absolutely destroy a person's life.
Likewise, friendships can be extremely rewarding. An intimate, loving, loyal, devoted friend is a tremendous asset. Good friends can steer you in the right direction. When you have a wise friendship with someone, that friend will probably motivate you to want to do your best. There is something about close friendships that is encouraging and motivating.