Source: Episode 6
Scenario: Rei and Shinji just finished battle with Ramiel. In order to protect Shinji while he gets a second round off against the angel, Rei had to put her life on the line by using her Unit 00 to block a return shot from Ramiel. Shinji opens her capsule, burning his hands - just like his dad did - to make sure she's okay. "Don't say that you have nothing else... Don't say goodbye when you leave on a mission. It's too sad."