How can understand your own personality improve your relationship with other?

Understand you own personality can improve your relationship by knowing what sort of person you are and how you will react in certain situations or with certain people.
An example will be like:
I tend to be negative around people and have negative opinions.
You're a innocent, happy, bubbly person that has no worries.
Know that I'm that kind of person, while talking to you I'll avoid being negative so I wouldn't hurt you or offend you in anyway and we'll remain a good relationship.

Pardon me. to answer questions like this, we would have needed more information. for starters, two sentences from the excerpt that came with the question.