In the same way in which a check made out to two people cannot be cashed without the endorsement of both people, so our joint-heirship with Jesus cannot be taken advantage of without our cooperation. Unaware of this, many Christians are just trusting that the Lord will produce the benefits of salvation for them. They are aware that they can do nothing without Him, but don't realize that He will do nothing without us (Ephesians 3:20).
The idea that God will do exceeding abundantly above all that we ask or think, PERIOD, is not true. He has power, but it is the use of His ability combined with the power that works in us. "No power working in us" means no power of God will come through us. The exceeding greatness of His power that is to us-ward who believe is power that is not external, but is internal, within the believer. It is working according to the faith that we exercise in Jesus. It was this principle that Paul was stating when he said, "I can do all things through Christ which strengtheneth me."
The way we place our endorsement on the check is to believe what God promised in His Word and act on it as if it were true. IT IS! Jesus has already signed His name to every promise in the Word. We aren't waiting for Him. He is waiting for us.