It means to make a bitter decision get sour over making a said decision than getting the sweet reward of doing so
its an extension of Bitter Sweet with an extra step for more complex situations
Before: "i know it was the right decision but it felt so bitter and i'm really sour about it"
After: "I got the sweetness in the end"
(Bitter sour sweet)
A person you hate intensely not because they deserve such hatred but because they serve as a focus for your general hatred. A healthy way to dispense with excess animosity.
Jake's not really that big an asshole. He just serves as my hate sink.