It's generally best to err on the side of not sharing too much.
Sometimes work friendships transcend business and turn into long-lasting relationships, but often they're the result of spending 40-plus hours a week in proximity to someone who shares common goals and common frustrations.
It can be especially tricky to know what to share with your boss.
No matter how much you like your boss and how much you might consider your boss a mentor, she should be your supervisor first.
And friendliness should come second—and, if you get into a tough situation at work, will almost certainly come second.
You don't want to be in the position where information you've shared with your boss during a casual moment impacts your employment negatively.
What to do if your boss is nosy
Just as it's in your best interest to establish boundaries with your boss, it's to your supervisor's benefit, too—but not every boss realizes that, and under most circumstances, you're under no obligation to share personal information.
You can simply request time off for an appointment and not get into specifics, or say you're feeling under the weather and not share the gory details.
(Of course, your employee manual will specify when you might be required to provide medical documentation for absences.)
If your boss keeps pressing you for personal details, try redirecting the conversation to work matters.
For instance, if your supervisor's agenda for your Monday morning check-in seems to be a blow-by-blow account of your respective weekends, and you don't want to share, keep your answers brief and general.
You can redirect to your work priorities to the week ahead and most people will get the social cue and stop asking.
Some people don't pick up on signals, though. If that's the case, you might have to be direct with your boss and say your preference is keep work and home separate.
You have every right to do so.
You might ask if your boss has concerns about your work. Unless your personal life is interfering with your ability to do your job, it's your prerogative to keep it private.
What to do if your personal life is interfering with work
In some cases, however, you might need to share how a personal situation is affecting your ability to do your job.
Say a family member is ill, or you're getting divorced.
If this is the case, consider meeting with your supervisor or human resources to discuss potential solutions.
Come to the table focused on how your situation is affecting your work, and present possible remedies to help you get past the problem.
HR will be able to advise you on options such as unpaid, protected leave available under some circumstances through the Family Medical Leave Act (FMLA).
When accessing such leave, however, you will be required to present medical certification, but your employer is legally required to keep it confidential.
No matter what your situation is, remember you should never feel pressured to share personal information.
And, if you are a "sharer," remember your priority at work is always getting the job done—and not interfering with your colleagues' ability to do their jobs.
If you need to talk, it's better to find a close friend, family member, or even a therapist.