1. You are unique and special. You are the only you in existance. There is no one else like you. You live in a galaxy full of stars, yet you happen to live on this particular planet, with your own hair, your own life and your own way of thinking. Everything you do matters, because everything you do, think and be is unique. No one else can be you, except you. What you do matters.
2. You are not unique and special. There are over 6 billion humans living on this planet right now, just like you. Millions of people have lived before you and millions will live after you. There are thousands of stars in the universe. There is no point in trying to do or be any different, because everything has already, or will be, done by other people who can do a much better job than you. Nothing you do matters
Here is where it gets interesting. If nothing I do matters and I decide to - for example - smile at someone one morning, what does that mean? I don't have to smile at them - nothing I do matters. But the fact that I chose to smile at them, when nothing I do matters, means that I have chosen to exert myself for no other reason than I want to. What does that say about my regard for the person I smile at? What effect does it have on them? It makes it kind of special. It matters.
No matter what your view on your relationship with the universe, your actions matter. They make a difference. You matter.
Nothing nice or good has to happen. But it does. As my sister says, it makes everything good better.