Silence is a sword in the spiritual struggle. A talkative soul will never attain sanctity. The sword of silence will cut off everything that would like to cling to the soul. We are sensitive to words and quickly want to answer back, without taking any regard as to whether it is God's will that we should speak.
A silent soul is strong; no adversities will harm it if it perseveres in silence. The silent soul is capable of attaining the closet union with God. It lives almost always under the inspiration of the Holy Spirit.
God works in a silent soul without hindrance.
Divine Mercy In my soul
Book I, Page 3