Great faith was defined by Jesus several times in the Bible. In each of the cases, it was in seeking healing:

Jesus healed a Centurion’s Servant (Mathew 8:10).

A woman of Cannan asked for healing of her daughter who was demon-possessed (Mathew 15:28)

Do we believe that Jesus heals today? Do we have great faith? No matter what you are going through, you need to declare that you trust God. 

“And those who know Your name will put their trust in You; For You, Lord, have not forsaken those who seek You.” Psalm 9:10