Here are some other encouragements I've found to be emotionally honest in prayer.
1) Psalm 22. We usually read it as a prophecy of Jesus' agony on the cross. It is that, and more, I think. "My God, my God, why have you forsaken me? Why are you so far from saving me?" When it really really hurts, saying so to God is not a lack of faith, but is the response of faith. The Psalmist tells God "I feel really, really alone" then reminds himself who God is and that this feeling of abandonment won't last forever.
2) The song "Never Alone" by Barlow Girl. (listen here). "I waited for you today, but you didn't show", followed by "I'll hold fast to what I know, you're here and I'm never alone." The same cycle of expressing the feeling of abandonment then reminding yourself God is with you that David shows in Psalm 22.
3) A quote from Augustine's Confessions in the 4th century.
It is then our affections which we lay open unto Thee, confessing our own miseries, and Thy mercies upon us, that Thou mayest free us wholly, since Thou hast begun, that we may cease to be wretched in ourselves, and be blessed in Thee;
I'd paraphrase those words like this: "We lay our emotions open to you, confessing our weaknesses and difficulties, that you might free us wholly; trusting not our own ability to manage our feelings, but your ability to manage our feelings."
4. From the Westminster Catechism:
Q. 98. What is prayer?
A. Prayer is an offering up of our desires unto God, for things agreeable to his will, in the name of Christ, with confession of our sins, and thankful acknowledgment of his mercies.
5. Speaker Sy Rogers describes a dialog with God about his evil thoughts: "Why don't you do with your filthy nasty thoughts what you have never dared do. Why don't you just admit them and submit them to me." (The part I'm quoting starts just after 3:00 in the video.)