Un-syncing macbooks

I had a macbook air and recently got a macbook pro. I want to use the air for work and the pro for personal stuff. They seem to be synced together in the sense all of my files, data, etc. are on both, no matter which computer I saved it to. How can I undo this? I do not want the macbook air to have any personal documents on it since it is being used for work.

Thanks in advance