Do not go after the past,
Do not lose yourself in the future.
For the past no longer exists,
And the future is not yet here.
By looking deeply at things just as they are,
In this moment, here and now,
The things to watch are comparative judgments, thoughts and worries. I don't think you need to watch any in the physical world of form. I'm looking at a computer right now but it's basically empty until I employ the keyboard. Observing doesn't effect any object. If you watch from within the activity of the mind does the work of Buddha.