why being alone, apart is essential

"When you have moved into a deep relationship with somebody, a great need arises to be alone. You start feeling spent, exhausted, tired -- joyously tired, happily tired, but each excitement is exhausting. It was tremendously beautiful to relate, but now you would like to move into aloneness, so that you can again gather yourself together, so that you can again become overflowing, so that again you become rooted in your own being.
...Love arises out of aloneness. Aloneness makes you overfull. Love receives your gifts. Love empties you so that you can become full again. Whenever you are emptied by love, aloneness is there to nourish you, to integrate you. And this is a rhythm...
Love is a spontaneous phenomenon. Whenever it happens, it happens, and whenever it doesn't happen it doesn't happen...
When I want to be alone that does not mean that I am rejecting you. In fact, it is because of your love that you have made it possible for me to be alone...so that he can again gather together his being, so that again he has energy to share. And this rhythm is like day and night, summer and winter; it goes on changing..."
Osho, "Intelligence"