Moses was the only prophet to whom God spoke directly, just as a person would converse with a friend. However, this uniqueness went only one way; every single human being has the ability to speak to God directly, "as a person would speak to a friend." Indeed, we should do so.
In this way, we can fully express our innermost feelings. True, we address God as the King of the Universe, which He is. We also plead with Him as a child does with a parent, which He is. But we certainly would never tell a king everything about ourselves, and we all have things which we would never want our parents to know. With a friend, however, we have fewer restrictions and less resistance. We can reveal everything to a friend, even things that we would be too embarrassed or otherwise reluctant to tell anyone else.
The Torah refers to God as "a friend" (e.g. Proverbs 27:10), because it wishes us to have this relationship with God, as well as that of subject to sovereign and child to father.
One might ask, "Since God knows our thoughts, why should we reveal them to Him verbally in prayer?" The answer is that by doing so, we reinforce our relationship to Him as a friend.
When you complete your formal prayers, add some of your own composition, and speak to God as a friend.