“Between The Optimist and The Pessimist there is a droll. The Optimist sees the donut; The Pessimist sees the hole.” Another phrase more commonly known is “Is the glass half empty or half full?”
How people process and react to information is different, and in a way, it’s quite fascinating. We also have people who struggle with relating to others that are different in the terms of introversion/extroversion, as well as other other categories.
You have really hit the nail on the head by saying, “I have learned that people like this will always continue to view life in general as grim.” It comes down to that this is the way that they are wired. It doesn’t make it right or wrong…it just is. In my experience, you cannot change another’s actions, much less their thought process. The best that can be done is set an example that will inspire, but this doesn’t mean that it will motivate them to change. Some personality traits are just so ingrained that a person can learn to adapt, but it won’t change the innate thought process.
So, back to your question on how to deal with it. It really comes down to learning that other people are different, and focusing on accepting how they respond without taking it to heart. If you really want to learn how to deal with this, I suggest that you read The Platinum Rule. Here is one quote from this site: The goal of The Platinum Rule is personal chemistry and productive relationships. You do not have to change your personality. You do not have to roll over and submit to others. You simply have to understand what drives people and recognize your options for dealing with them. I read the author’s book and found it to be one of those “ah-ha” moments in understanding why treating others as I want to be treated often fails.
Another recommendation is to watch this clip from public speaker Amanda Gore. Interestingly, she uses some of the same words as you do in your initial question. I’ve heard her speak several times, and when it comes to this part, she refers to how to deal with “Energy Suckers” a.k.a. “Psychic Vampires”. Note: This isn’t the best example of her presentation, IMO, as it becomes a plug for the props that she uses and now sells, but the message is still valid.
I hope this helps. Just know that my heart goes out to you and to the others that feel the same way. It is a painful position to be in, especially if it involves a loved one.