If you didn't truly exist then, you couldn't question your own existence. Do you hurt inside? Are you able to feel physical pain? Clearly you're capable of thought or you couldn't be asking these questions. Are you the one who chooses what you will or wont say or do? That is reality. I'm overly self aware which makes me want to question the existence of others but, after many years of being dominated by this irrational feeling I now do accept others as real. The only way that you could not be real would be if you were a fictional character or part of someone's dream. Your life isn't written like a script. You are the ruler of your life. You are the one who makes the decisions and directs it. Pinch yourself hard. Did that hurt? Can non real people feel pain?