Jimmy Bagwell makes specific suggestions on developing one’s prayer life, including this one:

Pray for anything that is on your heart. You may feel the need to express deep dark emotions; this is perfectly fine. Jesus is our example of this. Many times he expressed his negative and hurt feelings in prayer. The secret is to always end with a positive thought. On one occasion Jesus expressed his angst and emotional distress with the phrase “Let this cup pass from me”. In so doing he poured out his feelings of remorse and sorrow but he ended with a positive thought; “Not my will but yours be done”. We must do the same. Those deep dark emotions, those feelings of despair and depression should be shared with God.