Our forefathers demonstrated and developed their trust in G-d as they shouted out to Him. As a result they stood at Mount Sinai and received the Torah.
baavor avosanu shbatchu bcha vatlamdenu chukei chaim
translated: for the sake of our forefathers that trusted in You, and You taught us the laws of life.
Shouting out to G-d in one's privacy is a way of developing trust in G-d. This is in addition to meditation, public prayer, Torah study, performance of mitzvot.
- adapted from R. Miller's Serving by Prayer