Many people do not like addressing mental health issues. Despite the fact that so many people either have a mental health issue, or are affected by a person dealing with such an issue, people remain scared of talking about it, un-educated, and believe they are doomed to isolation about their realities.
I like the way this the NMHA puts it: people spend much time "denying the warning signs, worrying what other people will think because
of the stigma, or wondering what caused your loved one to become ill." http://www.nmha.org/go/information/get-info/mi-and-the-family/recognizing-warning-signs-and-how-to-cope
Denial doesn't help anything. You can seriously mess yourself up to where you doubt reality, and what's actually going on, and struggle more because of unvalidated feelings. It's better to address what happened, and not pretend you're not really hurt by what happened, angered, disappointed, or even scared - at least to yourself and trusted people. Probably best to not discuss these things with the mentally ill person - if they are the type to use your being scared, angry, or hurt against you.
Worrying about what other people think
Most people won't understand what you're going through. Most people won't have anything relevant or nice to say. But your closest friends or select people can at least hear you out and keep you focused on things outside of the issues that may seem to take up your whole life. If you worry what other people think too much, you'll end up isolated. You'll end up spending a ton of energy hiding the reality you live in, instead of being supported. It's better to have a shorter answer for people who obviously aren't going to be close confidants - "So and so has a lot of personal challenges." What kind? "They are quite personal, but I appreciate your concern and friendship."
Wondering what caused this
Even if you decide you know the source - genetics, drug abuse, etc. - one can often wonder, "if I had just done x, y, and z, would this have not come about?" Especially in a particular situation, "If I hadn't mentioned going to the store earlier, would there have been a fight?" this constant second guessing or endless attempts of personal behavior modifications of the healthy members' to try to avoid incidents / episodes with the mentally ill person - end up being a burden and don't usually solve much.
Not denying the warning signs, seeking support, overcoming the fear of what others think, and taking the pressure and blame off of yourself are ways to cope with situations involving mentally ill family members.