As you approach the speed of light, in any direction, due to time dilation, once you get above 0.866 c, as you add thrust, it still seems like you're accelerati

As you approach the speed of light, in any direction, due to time dilation, once you get above 0.866 c, as you add thrust, it still seems like you're accelerating normally, but you are instead accelerating yourself more in the time dimension than in a spacial dimension. Time continues to slow for the rest of the universe from your POV, until you reach 0.999... c, at which point time you are moving so fast, the rest of the universe appears to not experience time anymore. The same as how galaxies at the edge of visible universe are receding away from us at the speed of light, and are deeply redshifted, but if we could correct that redshift, we would see galaxies that don't experience time, because they are moving away so quickly, that we are receiving their photons at a heavily reduced rate. Photons do not experience any time, from their POV, they are created and destroyed at the same time. Thus going FTL implies travelling backwards in time.