Your mind is not original to you. At least the way in which it is functioning right now is not. Throughout the course of life, what we call our minds takes many shapes. It is in no way consistent enough to be a representative of self. After all, to be called a thing, the object must be consistently that. And yet, despite its constant shape-shifting, most of us take its content to be the sum total of who we are. It is no wonder how throughout the ages people have complained about the voices in their heads. How are you ever supposed to know who you are when the thing you consider to be yourself keeps changing?
One piece of evidence which allowed me to start to pick up on the inconsistencies of mind is the fact that I primarily think in English. English is not my first language. There was a time, about nineteen years ago, when this mind could not have existed because English was not yet a part of my experience. There was a time when it must have been a Spanish mind. And before that, it must have been a language-less mind.
Observing this has allowed me to see that mind is a process that has developed within me, but it is not me, because all throughout its development I have been there to watch its functioning change, according to many things. It is a responsive mechanism. As its environment changes, so does it. But I, the observer of mind, have not changed. All throughout, it is the mind that has felt the need to change and adapt to its circumstances, it is the mind who has wanted to strive and survive; it is the mind who has feared death. I simply observe.
I have witnessed the births and deaths of many minds. As the scenery changes, so does it. It is part of the scenery, in fact. I have peacefully just observed, like a child watching television from his sofa, in the safety of his living room, never once fearing death for a moment.