26 years ago, the Voyager episode "Threshold" aired, in which it was revealed that humans who break the Warp barrier turn into lizards. This episode has been wildly reviled, but those protesting it are missing an important truth.
Every single time a human breaks a speed barrier, they turn into a lizard. It's a biological fact - in attempting to break the sound barrier, we went through sixteen test pilots before Chuck Yeager mysteriously didn't turn into a lizard. There is ample pictographic evidence to show that the first humans who attempted to ride horses turned into lizards. Our simulations show that we can expect the first team of astronauts attempting FTL travel will turn into lizards.
When faced with a velocity that the human brain is unprepared for, a complex psychosomatic process is initiated and the human turns into a lizard in response. After the new "maximum" velocity is normalized and no longer seen to be excessive, humans stop being startled by the travel velocity and cease turning into lizards. It's just basic biology.