She's at her best when 'the heat is on'. [=when she feels a lot of pressure; when she needs to finish something quickly]
She said things in 'the heat of the moment' [=when she was angry for a short period of time] that she later regretted.
The company has 'turned up the heat on' [=has put extra pressure on] its employees to finish the job quickly.
(..) You know what I've learned, Marcus? Is you can focus on what is lost... ...or you can fight for what is left. I'm a little cold. Relax. I just want some body heat. You have a strong heart. God, I love that sound. Thank you for saving me back there. l don't meet a lot of good guys these days. (..)2009 Terminator Salvation