A person cannot obviously tell what is someone else's heart but they can tell what is their own. Yet people spend most of the time in worrying about others opinion and what others might be thinking about them. THis is a futile exercise and something that is completely against our nature. When you don't find the answers, you make them up in your own mind which further pollutes one's mind.
Marcus encouraged self dialogue and his writings 'Meditations' is exactly that. We can see the aspects of his self discovery within his book and it is inspirational for me as to what can be achieved.
Another important element to consider to act according to our nature. This action of curiosity of what is happening is someone's sole resulting in unrest is against our nature and can only happen in the absence of use of reason. We should not give into our impulses but always be exercising reason to dictate our actions.
Marcus Aurelius and the Stoics in general focus on Self-Awareness. One of my favourite authors who has done great work in the recent years in popularising Stoicism is Ryan Holiday. His website is a great source. A relevant link is provided below.
How to
The moment such thoughts come to your mind, redirect your attention to your own mind. This cannot happen over night and a conscious effort needs to be made to redirect the thoughts and train your mind.
Parh parh ilm hazaar kitaaban; Kadi apne aap nu parhya nahin (Bulleh Shah)
Translation and Explanation:
You read thousands of books to call yourself knowledgable, yet have you ever dedicated any time to getting to know yourself