The Bolton light-welterweight, 25, has suffered two huge setbacks over the past 11 months. He controversially lost on points to Lamont Peterson in December and was then knocked out by Danny Garcia in July.
"There's always pressure when I fight but I definitely have to win this because if I lose, I'm done," said Khan.
"This is a fight I need to win, 100%. If I don't win it I'm done. It's that simple.
"The big super-fights I've always dreamed about won't be there if I lose this. Pacquiao, Mayweather - forget it."
Khan and the unbeaten Molina go head to head at the Los Angeles Sports Arena on December 15.