2 Thessalonians 1:5-7

This is evidence of God’s righteous judgment, to make you worthy of the kingdom of God, for which in fact you are suffering.  For it is right for God to repay with affliction those who afflict you,  and to you who are being afflicted to give rest together with us when the Lord Jesus is revealed from heaven with his mighty angels.

We are grafted into the "family" that is the Trinity: God the Father, God the Son, and God the Holy Spirit. In Christ we are united with God, and God is able to reside in us via His Holy Spirit. Because of this relationship, and the resulting gangbuster overflow of grace, mercy, and good works. Yet even though God's goodness is apparent in our walk with Him, there are times when we are afflicted with some kind of persecution for the name of Jesus. We suffer for the name of Christ, yet we will have rest together with Jesus! That is the promise!