Hi Nodrama,
I'm certainly no expert in these matters, but I can see why this might occur in your case.
First, please allow me to give you a closely-related analogy. I am currently writing a book entitled "The Stigma of Mental Illness - Been There, Am There...Maybe I Could Help?" Now, when I am writing content for this book, it is somewhat therapeutic for me as i do suffer and have suffered from mental illness. But, on the other hand (and this is where the analogy to your situation comes in), I get depressed myself and upset, especially with all the misunderstanding and cold-hearted comments (i.e. stigma) from people towards mentally ill people, while they themselves have never suffered a moment of mental illness in their lives, some of whom are my own family members.
The other thing I might throw out there for you to consider as a possible cause is this: You may suffer from what I have, which is obsessive compulsive behavior or disorder. So, you "fixate" as your friend suggests. It's like you can't change your thoughts or your mind, no matter how hard you try to, and you continuously play back what you have just watched or read over and over and over again. You see these other people struggling, and then you feel a connection with them. You have an affinity (are sympathetic) with their struggle.
Finally, there is a popular saying, which might be applicable here in your case as well: "Misery Loves Company." Not saying this has anything to do with "misery," but I am saying that the expression can be interpreted to mean that, as I wrote above, people who are going through the same struggle tend to flock together."
My two cents worth.
