Have you ever heard of bipolar disorder disease?

You deal with it with understanding that it is not completely in their control. Educate yourself about what bipolar disorder is. And, by the way, there is no need to add "disease" to the title of the illness. Have you ever had an extremely bad day when nothing seems to go right? Try having those days all the time and praying to God to take this affliction from you because you can see the hurt in your loved ones eyes every time you snap at them. The smallest things irritate you as if you've been through extreme stress 24/7 for an extended time, even though you know life is actually going pretty good. Bottom line, do not take it at face value. If it is someone you are close to, catch them when they seem to be in a fairly stable mood and explain to them your concern and use "I" messages. Do not accuse, do not finger point. Ask them if they'd like for you to help with anything within your powers to do so. Ending the stigma of this and other mental illnesses can be helped by doing your part as a decent human being.

I know someone with bipolar disorder. He can be so sweet and caring at one moment, and suddenly he gets so mad and angry. He is taking medications now. His friends and relatives know of his situation so we understand him. Others who do not have an idea of his condition stay away from him because of his sudden change of moods. It is also sad because he tends to shy away from people and does not want to make new friends anymore because of his fear that they will pass a wrong judgement on him.

But there is a valid reason...they have a mental illness. There are medications that can help. If it is a friend or family member you are speaking of, and they are not under medical care, I suggest you find a way of convincing them to seek help.