It all comes down to infinity. Theoretically, if we could build a ship strong enough, we could fly at 99.99999999999% the speed of light. Forever getting closer, but never actually achieving it. Infinity is a hard concept to grasp, but once you achieve the speed of light, everything becomes infinite. (At least according to relativity). That means your mass would be infinite. You would have length contracted to zero (Infinitly thin 2 dimensional object). You would appear as if time had stopped completely for you (Frozen infinitly). we cant get to infinity as far as our mental capability is concerned. Someone on here even said something else though I cannot remember who. It was a good point. Your gravity would become infinite, therefore everything would accelerate into you at an infinite rate. You would become a singularity. A black hole the size of an infinitely small point.