Since Steve Evans' departure at the beginning of April Crawley have only collected five points from a possible 12.
The Reds have to win at Accrington on Saturday to be certain of pipping promotion rivals Torquay and Southend to third place.
"We're all nervous. There's no 'get out of jail' card after this week," Carter told BBC Surrey.
"Nobody will be more disappointed than me if we don't win. But would it be the end of the world? No, it wouldn't.
"We've done extremely well and it has been an amazing season."