The Faith Way
This verse in Rev. 3:20, although religion applies it to sinners, is in reality addressed to believers. "Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me."
The picture I see here is that believers have shut Jesus out of their heart by opening it to the vain philosophies of men. The faith door of their heart is closed. In their religiosity they try to muster up enough faith to open their hearts door and gain access to God's presence to make their demands of prayer and lay claim to being a person of great faith if they get an answer to that prayer, no matter if the answer is from God, natural healing, or deceiving spirits.
In the midst of all our religious activity God is gently knocking on the door of faith to our hearts so He can come in and sup with us and us with Him and in doing so, bring His blessings because "in him all the fullness of the Godhead dwells.
It is not that we get to God by our faith...it is that God gets to us by our faith! Faith's only role is to let God in, and when He is in, we have anything and everything we need!
We have simply to open the door and let the grace that has always been there, welling up, come flooding in, filling our hearts and lives with the presence of Christ and His blessing.
“If any man open the door, I will come into him.”
Ponder carefully every word here. There is nothing saying our praying is what draws Jesus into our hearts. Nor is it our prayer which moves Jesus to come into our hearts. All He needs is access. He enters of His own accord because He desires to come in. And He enters in wherever He is not denied admittance.
As air enters in quietly when we breath, and does its normal work in our lungs, so Jesus enters quietly into our hearts and does His blessed work there by opening the door of faith.
I trust that you can see now how you can pray continually, prayer is nothing more involved than to let Jesus into our needs.
Faith is simply trusting Jesus by opening our hearts door of faith and supping with Him and He with us.