God is good. That is one of the most basic messages of Jesus' Sermon on the Mount.
What does Jesus teach us to have in mind as we pray? That God is good.
When Jesus taught his disciples to pray, we remember the words of that prayer and pray them. But first he made sure they understood why he taught us such a bold but simple prayer:
"Your heavenly Father knows what you need before you ask him" (Matthew 6:8).
Jesus taught us to call God "Father" when we pray, so that every time we pray our first thought is that our heavenly father knows what we need before we ask him.
"If you, even though you are evil, know how to give good gifts to your children, how much more will your Father in heaven give good gifts to those who ask him?"
Why does Jesus urge us not to worry? Because God is good.
"Look at the birds of the air. They do not sow crops or harvest or store away in barns, and yet your heavenly father feeds them. Are you not much more valuable than they?"
"See how the lilies of the field grow. They neither toil nor spin (neither work nor weave). Yet I tell you that not even Solomon in all his splendor was arrayed like one of these. If that is how God clothes the grass of the field that is here today and tomorrow used for fuel, will he not much more clothe you, O you of little faith?"
"So do not worry, saying 'What shall we eat?' or 'What shall we drink?' or 'What shall we wear?' The pagans run after these things, but your heavenly Father knows that you need them."
How can Jesus tell us to be good even to our enemies? Because God is good, even to the unrighteous.
"I tell you: Love your enemies and pray for those who persecute you, that you may be children of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous. ... Be perfect, therefore, as your heavenly Father is perfect."
Because God is good, we need not worry. Because God is good, we can pray. Because God is good, we love our neighbors.
"This, then, is how you should pray: 'Our Father in heaven ...'".