We often struggle to trust people. This is probably because, as people, our acts are often motivated by selfish desires. This lack of trust can transfer over to how we relate to God. We need to understand that God is not motivated by selfish desires but by self-sacrificial love. This makes Him completely trustworthy. "The Prodigal Prophet: Jonah and the Mystery of God's Mercy" by Timothy Keller was a great resource in building this series.