Amulek's use of language is not accidental. He has suggested crying unto God in several different circumstances. Yet, in this verse, he does not use the phrase "cry unto him." Rather, something more cathartic must take place in our closets. This is where the real emotional energy is expended. And so, the image is that we "pour out our souls" like water out of a pitcher. The pitcher is empty after the pouring. This signifies that nothing has been held back or hidden. We have been completely honest with the Lord and ourselves. It is the time of greatest spiritual vulnerability and honesty when our will has been submitted to the Father's. As in all things, the greatest example comes from the Savior, who in the Garden of Gesthemane, poured out his soul unto death (Isa 53:12).
Elder Francis M. Gibbons
"Satan and his followers, who have been cast out of God's presence and are dead to His spirit, are excluded from those who, by the spirit of prophecy and revelation, may know the thoughts and the intents of our hearts. So, in his wisdom and mercy, God has provided a channel of communication between him and his children on earth that Satan, our common enemy, cannot invade. This is the channel of secret prayer. The significance of this to the Latter-day Saint is profound, for by this means we are able to communicate with our Heavenly Father in secrecy, confident that the adversary cannot intrude." (Joseph B. Wirthlin, Finding Peace in Our Lives, p. 163)