I hate dreams where something happens to Tara (my sister). I still vividly remember every nightmare I've ever had where anything bad happened to her, was going to happen to her, or might vaguely have had something bad possibly happening to her. I think I would truly die inside if something bad happened to her. I might physically survive such news, but I wouldn't really be alive anymore.
One nightmare I had once had Tara kidnapped by a serial killer. I was playing along with his demands because it would get me close to him. I was planning to kill him and rescue her. I remember thinking I wasn't going to survive the rescue attempt, and I also remember being like, "Then so be it." All that mattered was stopping him; if I died saving my sister, then it would be a good death. When I woke up, I thought about it, and decided that the dream did a perfect enactment of what would happen if I found myself in that situation. I truly would die if it meant saving Tara from harm.
Luckily, this last dream makes a grand total of about 4 or 5 such "Tara in danger" dreams since her birth 18 years ago. But I've cried in dreams before, for other reasons.