As many people increase their level of awareness and becoming happier and happier, they begin to notice the weightiness of the interactions with someone in their life.
How do you deal with such a person?
To manage difficult personalities, you have two choices. The first is obvious - decide that this person's influence is repeatedly detrimental and eliminate the person (extreme) or their influence (by not discussing certain matters) from your life. This method is impractical in most cases - but in certain situations is the best course.
However, a less permanent or difficult manner is to discuss briefly the situation with the other person. Make the facts known. Do not expect any particular result - negative or positive - and allow the conversation to be just factual. If the difficult person is negative, simply state, "I appreciate your opinion, but I am happy with my view (or my decision, my choice, etc.)." Word your response however is natural to you but the key is to remain matter of fact and unemotional in your words and in your thoughts. After stating your perspective, change the subject quickly.
The other person will begin to realize that negative input is not finding a place to thrive within you. You are not seeking negative responses.
In the future, before you present information that you believe will be portrayed as negative, picture this person happily listening and being open-minded. Just picture it. It may not come true, but this habit allows you to begin to take control of interactions by not allowing your preconceived idea of negativity to influence the other person's actual reaction. You know that what you focus on expands. If you focus on the fact that this person is not supportive, that is what will grow. If you begin to focus on what you do want, that will grow in its stead.