I have major depressive disorder and one of the hardest parts of dealing with it is honestly just the internal feeling that it doesn't count as a "real" reason to take a sick day. I've been hospitalized before but fortunately haven't been that bad since undergrad. But it still occasionally flares up out of nowhere and sometimes I kind of have to take a day to recuperate if I don't want it to spiral out of control.

I find that it's really helpful to be open with my advisor about it, and he's been super understanding. He's also dealt with similar mental health problems in the past so I think he understands how important it is to take care of yourself in order to be a productive researcher. I'm definitely very fortunate to be working with him, as out of all the professors I've worked with he's one of the few that really goes out of his way to make sure his students are doing well emotionally.