The first thing that it appears to reveal about cummings is that he believes in God. He addresses the poem to Him, as a sort of oblation, a prayer of gratitude. He even opens up in the style of a prayer by saying "i thank You God for most this amazing day." So, he believes in God, and given the text of the poem, is grateful that God made such a beautiful day, a beautiful earth to live in.
Note also cummings' unusual use of capitalization when speaking of God. Cummings is famous for never capitalizing anything at all. He messes with the rules of standard spelling and punctuation a lot, and even in his own name he didn't capitalize. It is e.e. cummings, not E.E. Cummings. So, the fact that he deviates from his non-capitalization in order to write "God," shows the deep respect and reverence that he must have for God. He refers to God as You, with a capital Y also. Capitalizing indicates honoring someone that you respect and admire, and showing your deference for them.
In addition to his belief and reverence for God, we can tell that cummings enjoys nature and the beautiful things of the earth. It invigorates and enlivens him. The entire poem is a rejoicing of the beauty that can be found in God's nature.
I hope that those thoughts helped; good luck!