"I wish I had known that vulnerability is universal for everyone, regardless of how cool or not cool they are. You have such a heightened awareness of yourself, so even small things seem life-changing — a bad day turns into, 'Oh my gosh, my life is over.' If I were still a teen, I would want to hear: 'It's okay. Take a deep breath and move on,'" Penn Badgley tells Seventeen about advice he wishes he had been given growing up.