Religion is believing in a deity or deities. It is to believe in a supreme or at the least a superior being higher than ourselves. Being spiritual and believing all things are connected is not religion. But to personify spirituality does make it a religion. That is the only fine line.
You can be spiritual and be technically an "atheist" if you do not believe in a higher power. Having a belief or faith in something is not necessarily a bad thing. I believe and faith that one day I'm be a billionaire, own several tropical islands, and marry the girl of my dreams

Not that any of those beliefs in mine are rooted in facts. Which is the biggest discriminator. Which is being able to recognize what you have faith in may not be right because you have no facts to back up your faith.
I hope that answers your question. Again for technical definitions.
Religion = Theism = belief in a deity(ies)
Atheist = do not believe in a deity
Spiritualism without personification = Atheism
Spiritualism with personification = Theism