Toxic and Contagious Attitudes

Does everyone has pessimistic people in their lives? I have a few in my life that are just really hard to shake for one reason or another. Even though there are only a couple, and they aren't always negative (just most of the time) their unpleasant outlook on life is really contagious and after a short time of exposure, I feel like I am surrounded by bleakness. While I do love these people, I also can see that they can have really toxic effects on me. I don't know if I'm more influenced by negativity than anyone else, but I do know that a short time around bitter people leaves me feeling irritated and grumpy myself.

It seems to me a waste of the gift of life to walk around feeling annoyed and angry all the time, and I really don't enjoy feeling that way myself. There are certainly times when sadness or anger are valid and appropriate, but for the most part, I'd rather be laughing.

Since realizing the contagious nature of these toxic attitudes, I'm really trying to make a conscious effort to protect myself, and my family, because we all know that if Mama isn't happy, nobody's happy. I read something once about safeguarding our family from bad moods in the same way we would protect them from the flu. If you knew someone had swine flu or bird flu or whooping cough, most people wouldn't have their children spend a lot of time in close contact with the infectious person, at least not while they were ill. As parents, I would think that even if we were the ones with the contagious disease, we would want to limit our kids' exposure until we were better. The theory of applying this perspective to bad attitudes as well made some sense to me. Of course, we can't completely prevent kids from being exposed to all negative moods any more than we can keep them from ever catching a cold. I don't want to live in a bubble, but when the mood is downright toxic, I don't see a lot of benefit in making loved ones endure it.

I also recall reading that even though all kinds of moods can be contagious, bad moods permeate social settings sooner and last longer in social settings than good ones do. Since I'm not particularly organized or scholarly, I don't remember the sources to cite them, but they did appear legitimate to me and in any case, they made enough sense to me that I wanted to think about implementing the strategy in my own life. I know I'd rather have laugh lines than scowl marks on my face any day, and I'd much rather my children are surrounded by pleasant people than bitter ones. So, I've been looking at ways to limit exposure to toxic attitudes and people with them.
I think of this as a life skill, and I'm also encouraging this as something for my kids to think about when they choose friends, activities etc. While I have some control over these things in their lives now, they will be on their own someday, and I want them to have the skills to deal or get away from unpleasant situations and people. This will take practice for all of us I'm sure. Some cases and some people are just easier to avoid than others, so I'd love to hear how other people handle it. How do you deal with bitter relatives, negative neighbors, or just plain disagreeable, sour, poisonous or distasteful folks in your life- especially the hard to ditch ones?