There are a vast number of ways of conceiving of spiritual meaning or purpose in life. They do not all necessarily involve the concept of believing in "a supreme being".

If there were a supreme being, would it have to be seen as separate from oneself?

And if so, how would that be likely or even possible?

People operate on a great many assumptions, most of which they have thoughtlessly acquired when quite young from their parents, their society, their culture.

Most of those assumptions are arbitrary. Most of those assumptions are open to question, but most people never question them and they usually get upset if someone else does.

The one thing people are most afraid of admitting is this: how little they really know. This is particularly true of our highest authority figures such as scientists, doctors, politicians, military leaders, business leaders, and religious leaders. What they know is the tiniest fragment of what is out there to know.

They lack humility. They are afraid to admit to how little they know.