It is the highest act of which the soul is capable.

When you pray truly, all that is best, noblest, most exalted, purest, heavenliest in you, presses up toward God.

Hence earnest prayer always lights up the very face, and lifts up the life into higher, holier mood.

We grow toward that which we much desire.

Hence prayers for Christ-likeness have a transfiguring effect.
Holy thoughts in the heart have also a transfiguring influence on the life.