Holding on to anything is like holding on to your breath; you will suffocate. The only way to get anything in the universe is by letting go of it. Let go and it will be yours forever.
Can I be a Christian but still practice Buddhism? (since it's nontheistic and I'm not worshipping another God...)
Yes! It’s very common for people to practice Buddhism with another religion. Some even view it as more of a philosophy than a religion, it really just depends on how you view it.