The real purpose of this slogan is to pull the rug out from under you in case you think you understood the previous slogan.
Lojong slogan 3 is an examination of our inward world as opposed to looking outside ourselves as we did in slogan 2. It asks us to think about who is doing the observing; the age old question asked by philosophers, spiritualists, mystics and scientists. When we begin to observe our own mind we begin to change patterns- but not by creating new ones. Rather we dissolve the patterns of perception so we can be left with only what is real. We simplify who we are instead of over-complicating matters.
When you become aware of an object or person they seem quite separate and solid. Try to move away from the need for comfort and security that comes from perceiving this sort of solidity. Who is it that’s doing the observing? Who is perceiving? As we allow ourselves to step out into the unknown in this way we become liberated, we become enlightened.