P lay is usually physical. Our bodies are engaged. We move, we use our large muscles, we can sweat. P lay often involves a conscious abandonment of dignity, sometimes by putting us into roles or positions that are outside our usual behavior. P lay usually involves others.
Solitary play is OK if there is no one available, but it's more fun with other people.
P lay involves being spontaneous, doing what our impulses tell us. Spontaneity helps us lose self-consciousness, which seems to be a major point of play. I think the fact that animals play should tell us that play is part of nature, that we need to play to live. For the small indignities, the best remedy is a Charlie Chaplin movie.