First impressions can be quite important.
Everyone stereotypes everyone on first impression, even if we are reluctant to do it.
We all get a first impression of a new person that creates a mental image of his or her personality in our minds.
That image of you often lasts and can affect the relationship that follows.
Another thing is that we often play different roles in relationships. With our parents we play one role, with friends another, with someone we are interested in/in love with a third, when shopping for clothes in a store a fourth. And so on.