That is God's plan. It happens physically and it includes every aspect of our beings. God created sex for procreation and pleasure. It is to be enjoyed and experienced only in marriage between a man and a woman. Any variation of God's plan releases harsh consequences of eternal impact. Sexual relations are uniquely planned by God to literally join a man and a woman together as one.
But oneness in marriage is more than sexual union. It is oneness of every part of our being. We don't lose individuality but we blend into a union of common purpose. It is connection of life.
What are barriers to oneness?
Infidelity, selfishness, aloofness, criticism, and general lack of love.
The sad news is that because marriage opens the door to oneness that failure to care for the needs of the other actually hurts one's own person. When we hurt our mates, the truth is that we are hurting ourselves. The pain doesn't just affect the other. It affects both because you are not 2 but 1.
Women need love. Men need respect. Striving for oneness understands the needs of the other and works diligently to focus on those needs. That releases a return of love and life.
So women, honor, submit, and respect your husband with cheerfulness and regard.
Men love and cherish your wife. Make her know she is special, cherished, and secure.
In marriage we are one. It is God's way of blessing.