Let Peter describe the essence of saving faith...
And though you have not seen him, you love him, and though you do not see him now, but believe in him, you greatly rejoice with joy inexpressible and full of glory, obtaining as the outcome of your faith the salvation of your souls (1 Peter 1:8-9).
There are 3 things Peter describes in these two verses as aspects of the word "faith" and they all relate to the activities of the heart in relation to the invisible King and Savior Jesus.
1. You love him (v. 8)
2. You believe in him (v. 8)
3. You rejoice with joy inexpressible and full of glory in him (v. 8)
Peter assumes all those activities are involved in some measure in "your faith." No wonder it's a miracle. No wonder only God the Spirit deposited in us can pull this off. No wonder we need to recover this understanding of faith and share with the world that it desperately needs God's own power in them to produce a faith of love, belief, and joy in the living Christ to be saved forever.