Mark 11:23

I assure you and most solemnly say to you, whoever says to this mountain, “Be lifted up and thrown into the sea!” and does not doubt in his heart (in God’s unlimited power) but believes that what he says is going to take place, it will be done for him (according to God’s will).

Head faith is mental ascent with doubtful thoughts still plaguing the mind. Heart faith is invested in the word of God and His promises being fully convinced that God means what He says. Sounds simple but it takes knowledge from the word of God and development in our spirits. Faith can only work when it is poured into a vessel without any holes. Doubt, unbelief, and unforgiveness are holes leaking the Faith from the vessel.