I don't think people should be so strict as to think of a general rule. There are always exceptions and sometimes there are managers that you feel like you can

I don't think people should be so strict as to think of a general rule. There are always exceptions and sometimes there are managers that you feel like you can talk about anything with. The only things I could think of would be mental problems as I think many managers wouldn't have experience talking about these. A professional is much more suited for that. Even in this space, talking about a mental problem like burnout, might be acceptable if you have a *really* understanding and trusted manager.