As a person, we have 'personhood'. We're an entities and we think and feel using the mind that we possess as entities. As beings we have the qualities of 'beingness'. However, using an example, let's say, of an embryo - that never is born...that is miscarried and never is born... that embryo never lives. That potential life is now nothing - a non-existant being having the quality of 'nothingness'. It ceases to exist.
In my wallet, I have no money. When I have no money there, nothing exists there to spend. So, what is hard to imagine about those example of nothingness?