Jeremiah 1:12:

Then said the LORD unto me, Thou hast well seen: for I will hasten my word to perform it.

See also:

Say What
How Can I Get Rid of Unbelief?
I Believed I Received My Healing When I Prayed, but My Body Doesn’t Act Like It.  They Called a Healing Line.  Should I Get into It or Not?
Is “Seeing Yourself Healed” a New Age Visualization Technique?
Objection: Faith Must Be IN GOD (Mark 11:22), So It Is Not Something You Can Use Yourself to Change Things