And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with [him], that we may be also glorified together.
Note 34 at Ro 8:17: We are not just heirs; we are joint-heirs with Christ. How wonderful it would be to inherit any amount of God's glory and power, but to think that we share equally with the One who has inherited everything God is and has is beyond comprehension. This is an awesome blessing, but it places a tremendous responsibility on us too.
In the same way that a check made out to two people cannot be cashed without the endorsement of both parties, so being joint-heirs with Jesus cannot be taken advantage of without people's cooperation. Unaware of this, many Christians are just trusting that the Lord will produce the benefits of salvation for them. They are acutely aware that they can do nothing without Him but don't realize that He will do nothing without them (Eph 3:20).
The way we place our endorsement on the check is to believe and act like what God promised in His Word is true. Jesus has already signed His name to every promise in the Word. We aren't waiting for Him; He is waiting for us.