It is said that recognizing his Buddha nature took countless aeons for Buddha Shakyamuni to perfect. However, we are truly fortunate because the Buddha laid out a roadmap so our journey of discovery would have less obstacles. In his teachings, the Buddha mentioned that the true nature of our mind (or our Buddha nature) is clarity, compassionate and without boundaries.
It is eons of negative karma, delusions and all manner of reincarnations that clouds our minds, sets self-creating boundaries and makes us unnaturally self-cherishing. Hence, every person we know have somebody they cherish and care about. Even the most hardened criminal loves or cares about someone. That capacity for love and care is a reflection of the compassionate and true nature of our mind. In Mahayana Buddhist practice is to extend that love from our loved ones towards all beings through our spiritual practice. Unfortunately, many of us don't even know how to really love and care for those who are closest to us.
The true nature of our mind is clarity and that means having awareness of our ourselves, our surroundings, the people around us and most importantly, the effects of our actions upon others. Reflection, meditation and ultimately taking greater responsibility for our lives and others are great ways to extend this clarity. A person with great clarity sees not just people for who they are but what makes them suffer. That clarity drives these great beings towards working and benefitting more and more beings.
Last of all, boundaries are set in our mind based on our limited perception or rather of what we project our world to be. More often than not, our projections rule our lives and makes us miserable. True realizers of the mind contemplate the lack of inherent nature of projections and through practice of creating merit and meditation, they chip away at their projections until they realize 'emptiness'. I don't know enough on this topic to elaborate further.
There is of course much more than what I have laid out here but this is as far as I know. I am not realised any of them yet but i do hold a great fascination for this topic to retain some info.