If you're feeling a little anxious and you think "I'm feeling threatened", you are being mindful.
Being mindful, you observe the arising of anxiety and you think: "I'm feeling threatened".
If you think that your thought "I'm feeling threatened" is yourself, you're fooling yourself into believing "I'm observing myself".
If you think the arising of anxiety is yourself, you're fooling yourself into believing "I'm observing myself".
If you think that you're observing yourself feeling anxious, you're fooling yourself into believing "I'm observing myself".
When a thought "I'm observing myself" arise, you're fooling yourself into believing "I'm observing myself".
When any phenomena arises and you observe it, you're fooling yourself into believing "I'm observing".
Are you fooling yourself?
Your thoughts make you feel like you're not observing yourself, because if you actually were then there wouldn't be thoughts.
Your thoughts make you feel like you're fooling yourself into believing you're observing yourself, because if you actually were to observe yourself then there would be nothing to observe.
Just like when you throw a ball and you say to yourself "I'm observing the ball, thus I'm not the ball." in the same way you arise thoughts (or feelings, or anxiety, or any other phenomena) and say to yourself "I'm observing my thoughts, thus I'm not my thoughts. I feel I'm just fooling myself into believing I'm observing myself."
Find the cause of the arising of thoughts (or feelings, or anxiety, or any other phenomena), remove that cause and you'll know yourself.
In knowing yourself is the path to liberation.