The purest actions of the purest men need Christ to perfume them; and this is his office. When we pray, we need to pray again for Christ to pardon the defects of our prayers.
The Bruised Reed
Likewise the Spirit helps us in our weakness. For we do not know what to pray for as we ought, but the Spirit himself intercedes for us with groanings too deep for words. And he who searches the hearts knows what is the mind of the Spirit, because the Spirit intercedes for the saints according to the will of God.
When I don't know how to pray or what to say because the burden is too heavy and words fail me, it is with abundant joy that I submit to the work of the Holy Spirit in my life, allowing Him to 'perfume' my prayers with the Holy Spirit, who prays according to God's will always.