How would you explain Oneness to someone like me who is totally caught in feeling separate?
Every one feels separate to some extent because there is the belief that we are memory. However, your true essence is the same like everyone else. So, what makes you think you are a personal being is the idea that you are just a body forgetting the life-force essence. You are a human being. There are 6 billion humans on this earth but only One Being. We have forgotten the Being. Once we reclaim the Being that we are, which is One, then we discover the ultimate truth.
Attached here is a brief talk by Deepak Chopra who answers your question plus a few others.