"The mountains, the rivers, the whole earth, the entire array of phenomena are all oneself." If you can absorb the essence of this message, there are no activities outside of meditation: you dress in meditation and eat in meditation; you walk, stand, sit, and lie down in meditation; you experience joy, anger, sadness, and happiness in meditation.
To pray is to pay attention to something or someone other than oneself. Whenever we so concentrate our attention that we completely forget our own ego and desires, we are praying.