I usually don't share details of my private life with my managers. However, I had to tell my new manager that I'm undergoing a long, time consuming and painful therapy, because I need time off work for it. I was surprised by his extreme attention and interest to the issue: he often asks me how things are going, he's very supportive with me and he has never complained about my schedule. It's also true that I bring my laptop home often, to recover lost time. Anyway, up to now he had words of praise for my job, very differently from my old managers who very rarely praised me for my job. I guess this is just work culture being different in different places.
During these holidays, something very bad happened and I now have also a serious personal issue, on top of the health issues (let's say something of comparable gravity to a divorce, to put the issue into context). I feel devastated, and depressed.
My manager will surely ask me about how my holidays were: I've always thought I shouldn't tell him anything, and only mention the issue if it starts affecting my work life. However, reading this answer, I was surprised to see that the general suggestion is to disclose the issue before it affects the work performance. In my country, the usual suggestion is not to share private life details at work, because they could be used against you. If it helps answering the question, I can disclose which country my manager resides in, but I'd rather not disclose my country's identity.