The teachings of the Catholic Church on the reality of God might be summed up in the following points:
Prayer is commonly described as the activity of raising the heart and the mind to God. In other words, we take our thoughts and our feelings, and instead of following them where they naturally lead us, we try to focus them on God, thinking about God and feeling toward God.
In prayer, we try to think about God and feel toward God. The problem is that God, the Creator of not only the physical universe but of the very contents of our minds and hearts, is not present to us in the same way as anything else. Whatever we think or feel, God exceeds the content of our minds, cannot be captured in our imaginations.
In prayer, we think about God, and we feel toward God, and we use words to express what we're thinking and feeling, our needs, our desires, our hopes. So far, however, this is a one way conversation. As long as we're busy with the content of our own hearts and minds, we are unable to open ourselves up to God's invisible, inscrutable influence.