Also think about what happens when something travels at the speed of light (As yet proven to be physically impossible for something with rest mass). If you were able to achieve light speed, according to theory, observed in your frame of reference time would be dilated to zero and space would be contracted to zero. This is why the speed of light is a limit. There's no point in trying to achieve greater speed because it can't exist for the traveling you.
I do agree though that space-time is the governing factor rather than C. Space time shrinks to zero for anything traveling at C, or we could say that space-time expands for anything traveling slower than C. Where i get confused is if everything is relative then how does space-time know who is doing the traveling?