I always think of James Dean in "Rebel Without A Cause" when I hear that line... https://youtu.be/UBOcWFBBB04?t=79 "It's tearing me apart" is something you would say if you have two loyalties pulling you in opposite directions. For example, a married couple are always fighting with each other (like in the movie clip), and the son sees all this fighting. The boy loves both his parents but he is constantly forced to pick a side in the argument. The mother wants the boy to be loyal to her, and the father wants the boy to be loyal to him. "It's tearing me apart" means the boys love, and his loyalty, is being torn like it was a piece of paper, and one half of the paper ends up in the father's hand, while the other half ends up in the mother's. "I'm torn" is a much less dramatic example of the same thing. "What do you want to eat for lunch? Pizza or hamburgers?" "I don't know. I'm torn! I really like pizza but I love hamburgers. I can't decide, you choose for the both of us."

"It's tearing me apart" is different something that makes you sad, even something that makes you very sad. Someone says "it's tearing me apart" when faced with a grave/serious issue in their lives. Think about it, if you were to be literally torn apart, that would be quite serious, right? I say that to make a point, not to imply that people use this expression when literally being torn apart. The expression means that an issue is eating at someone's soul. It's a mind-consuming problem. It could make them sad, which is why it's tearing them apart, but it usually means more. Here are some examples in which this expression would be appropriate: >Someone committed a crime and nobody knows, besides the person they're telling about the crime and saying this expression to >Someone just found out their significant other is cheating on them but they haven't yet confronted them about it >Someone is waiting for the results of an important test (whether its a licensing exam, medical biopsy, etc.) >There's something on your mind that is bothering you and you can't think of anything else You'll also see this vary with age. A teenager will likely think that asking someone out on a date and waiting for their response is "tearing them apart," whereas an adult wouldn't. Those are just a few examples, and there are more many more where this would be appropriate. But as you can see, it's not an expression used lightly (unless as a joke). Save it for extreme scenarios/cases--something that is mind-consuming or eating at your soul.