As believers, we need to first understand that the entire scripture (including promise verses) is given by inspiration of God. It is given to us by the Holy Spirit and is useful one way or the other - showing us truth, exposing our rebellion, correcting our mistakes and training us to live God's way. (II Tim 3:16)
In the English translation of the Bible, the "Word" is translated from two Greek words "Rhema" and "Logos".
Logos is the inspired word of God and it refers to Jesus - In the beginning was the Word [Logos] and the Word [Logos] was with God and the Word [Logos] was God (John 1:1).
Rhema is the spoken word of God. Jesus said - The words [Rhema] that I speak unto you, they are spirit and they are life (John 6:63). More importantly, they are portions of scriptures that the Holy Spirit brings to our attention to face a particular situation in our life.
When we look at all the miracles that Jesus did, he spoke and the miracles happened. He spoke the Rhema word of God. Jesus is the Word [Logos] and there is power when we speak his Word [Rhema]. Secondly, he healed many because of their faith in him. And faith only comes through hearing and hearing by the Word [Rhema] of God.
The Bible clearly says that we need to take the "Sword" which is the Rhema word of God to quench the fiery darts of the enemy. Let us ask God to speak to us through his Word and let us use them to defeat every scheme of the enemy including sickness, pain, infirmities, tiredness, terminal illness, incurable disease, depressions, thoughts leading to suicide, barrenness etc.
Memorize Promise Verses
Finally, I strongly urge you to memorize as many promise verses as you can and read them aloud. We simply need to believe it and receive it in faith. Jesus has taken our curse, our iniquity, and our sickness onto himself and redeemed us when he died on the cross for us. Take communion daily discerning his Body and his Blood. Finally, rest in the eternal truth that - All the promises of God are fulfilled in Christ Jesus with 100% surety (2 Cor 1:20)