Freud's "oceanic" feeling and the Material World
First of all, this feeling does not pertain to the external Material world, but to the entirely internal Phenomenal World, the world as it is, but with the addition of all the notations, amendments, emotions, disappointments, joys, and hopes that an individual cares to attach to it. This is how the individual relates to the Material world, in that it is sensed, perceived, and given meaningfulness. The very sense of boundlessness and oneness -- unity or eternity -- with the stuff of rocks, trees, streams, and concrete, make the Phenomenal nature of this Oceanic feeling obvious in explanation and hindsight.
This also gives us the opportunity to explore the Protean character, the person who not only experiences this Oceanic feeling, but feels completely at home in it. Such a person can adapt a variety of attitudes and practices, and can emulate (act or role-play) other personalities, either for pure enjoyment and entertainment, or for the functionality and success that such a personality is perceived to experience in their particular endeavors.
The Phenomenal World of the Id, Ego, and Super-ego
This Phenomenal World then, with or without the presence of the Oceanic feeling of belonging, is the source of both our prolonged and predominantly subjective miseries and joys, as this is where the beneficial or hostile features of the material and dynamic world are recognized and labeled (or perhaps merely invented, whether out of positive or negative emotions and "Outlooks". P:D ) The purely physical world can harm us, but not insult us. That requires meanings that we ourselves give to it.