1 John 1:3 that which we have seen and heard we proclaim also to you, so that you too may have fellowship with us; and indeed our fellowship is with the Father and with his Son Jesus Christ.
What’s the difference between social interaction with someone and fellowship with them? The answer is spiritual. Fellowship is a spiritual connection between people that goes far beyond the social aspect. God is in the mix.
Those who seek after God’s will and truly want to follow after Christ as His disciples have to have a heart for discipleship. You can’t love God without loving other people. Our true fellowship is with God the Father through His Son because of His sacrificial atonement on the cross. We’d have no way to God the Father if it weren’t for Jesus. And our fellowship with God spills out into our relationships with other people.
Bottom line principle is that lack of fellowship with God equals a lack of true fellowship with people. We have to be spiritually connected to the Lord in order to have any deep interaction with fellow people. We have to put Him first and cultivate our relationship with Him or our other relationships will suffer. Our character, our attitude, our love, all are affected by our fellowship (or lack thereof) with God.