The phrase ‘If you can’t take the heat’ indicates that if one is unable to cope with a stressful situation, then one should leave it to someone else who can handle it. The expression is also commonly used as ‘If you can’t stand the heat, get out of the kitchen’.
Example in use:
Sam: “I’m really stressed about all the cold calling I have to do for work.”
Mark: “Maybe you should find a different job. You know what they say: If you can’t stand the heat, get out of the kitchen.”