I assure you, your existence depends on that grain of sand.
You're welcome to disagree, similarly as a child would insist on the existence of Santa Claus or a Christian on the existence of a paternal God-head.
Though that's not a perfect analogy, as proving either of those postulates wrong is impossible, and here we have a situation where there actually is strong evidence for the existence of sand granules (I hope you'll agree).
So in this case it actually is rather easy to see if you're correct. If you can "do just fine without it" then go and erase it out of existence. Come back when you are through and you'll have proven me wrong. :-)
You're welcome to disagree, similarly as a child would insist on the existence of Santa Claus or a Christian on the existence of a paternal God-head.
Though that's not a perfect analogy, as proving either of those postulates wrong is impossible, and here we have a situation where there actually is strong evidence for the existence of sand granules (I hope you'll agree).
So in this case it actually is rather easy to see if you're correct. If you can "do just fine without it" then go and erase it out of existence. Come back when you are through and you'll have proven me wrong. :-)