Apply this to our speech with God. What are our prayers to Him like? What comes pouring out of us is our heart—either that or God's Word is not true. What we are is revealed to God by what we say to Him in our prayer. We cannot hide it; we cannot be two-faced with Him.
Prayer is speaking to God what comes out of our heart. Even as this proverb Jesus gives is directed toward men, it is also true concerning our speech toward God. What we are comes out.
God wants His will done in every aspect of our life, and He wants our prayers to be according to His will. When we ask things according to His will, our requests stand the best chance of being answered positively. Why? Because, in effect, they are His thoughts coming back to Him. His thoughts having become lodged in our heart, we are now sending a part of Him back to Him.
We need to be careful not to think of this as a magic formula of some kind, as if we say certain words and out comes the desired thing. This is prayer—speaking God's words back to Him. These prayers have the best chance of being answered positively because it pleases God to see His children develop in His image. He then responds out of His love, even as we would to a child who pleases us.