Thessalonians 3:6

Now we command you, believers, in the name of our Lord Jesus Christ and by His authority, that you withdraw and keep away from every brother or sister who leads an undisciplined life and does not live-in accordance with the tradition and teaching that you have received from us.  

Influence from friends and relationships can indeed affect our thoughts, attitudes, and beliefs.  We seek approval from our friends and family, and what they think affects our decisions.  If we are trying to live a life for God but spend most of our time with people, who don’t, we will compromise our faith.