The first resurrection from the dead is Christ. He is being formed in us now. If He is not, then we are not attaining to the first resurrection. Either we are gaining the first resurrection today or else we are losing the first resurrection today. The Day of the Lord will not cause a change in our personality; rather, it will be an unveiling of that which has been wrought patiently throughout our pilgrimage on the earth.
If we are seeking the things that are above, if our attention, our love, our interests, our hopes continually are focused on the Throne of God, on Christ who is at the right hand of God, then we are attaining to the spiritual dimension of the first resurrection from the dead.