Your body is a system made up of smaller systems, each with several roles to play, sometimes overlapping and/or working in conjunction with each other.
For example, the respiratory, circulatory, skeletal, muscular, nervous, endocrine, digestive, lymphatic, integumentary, immune, urinary, & reproductive systems.
The body also has a hierarchy of systems which it is composed of. Going from largest to smallest, your: body, organ systems, organs, tissues, cells, organelles (components of cells), molecules, and atoms.
(At least, that’s our basic understanding to date.)
Now, on a larger level, the same thing applies.
YOU do not exist separately from your environment.
Of course you have your body, which functions apart from mine, but it is not completely separate.
We, as humans, have a role to play as a species within the larger ecosystem of earth.
But on an even more practical level, you can see this structure repeated again in your social relationships.
You might be some or all of these: a parent, child, co-worker, friend, sibling, role model, coach, teacher, neighbor, and more.
Sometimes it’s more than one, sometimes it’s with multiple people whom you share a particular role.
So remember, you never were, and never will be alone.
You always were, before you were born and even after you die, one part of a much greater whole.