laws of physics: nothing can fully disappear, niether can we

And so to find any plausible explanation of weather we disappear into nothingness after we die, I turned to one subject that was never explained to me well in school - physics. One law I do remember - matter can never disappear, regardless of what you do with it. Even acid only breaks it down into molecules. Our body remains here to enrich the soil for the future groves and eventually enters other human bodies through fruit and meat of the animals (ghastly, but a realistic thought - every time I bite on an apple, I get a piece of some dude from a thousand years ago), but what about our consciousness? It has to be of some sort of matter and according to the same law of physics, can not simply disappear. And so this fear of nothingness should be done away with - I, as I perceive and know myself, can not be gone, but only changed, who knows to what degree. First solid prove to myself, I shall never die.