In one breath we say "You can't judge a book by its cover" and then in the next we'll say "You never get another chance to make a first impression". While both statements have merit, they contradict each other.
As people, we are quick to judge other people we come in contact with, often without knowing anything about them at all. The person you think looks scruffy on the street may have been sitting bedside by a dying person and not had the chance to shower yet. Or maybe they worked a long shift and are headed home to shower...or they could have woken up that day and said "I don't feel like taking a shower today" and headed off because they don't expect to be judged by their appearance.
Yet we all judge by appearance....without knowing the background story or even if there IS a background story. Maybe that person you just met is quiet because they have social anxiety, or maybe they just got really bad news, or maybe they are in pain, or maybe they're introverted, or maybe they just don't have anything to say at the moment.
You can't know a person until you take the time to get to know them. Really get to know them. It is more than first impressions, more than what you've heard about them, it is taking an interest in what they have to say and how they say it. Ask them questions, watch how they act when they think nobody is looking.
If you don't take the time to understand a person, truly get to know them, you are doing them a disservice and yourself. You are only looking at your perspective and perception of what is going on with them, and not taking the time to find out if what you are assuming about them is true.
When you don't take the time to get to know someone, you could be missing out on an amazing connection. It is true, you could get to know them and absolutely hate them, and that is okay, but to instantly judge and dislike someone you don't even know causes you to miss out.
That person will continue on, making friends, having relationships, being a member of a family, without you. You may carry on without them, but you may be missing out on the opportunity to make a good friend, have an amazing relationship, or enjoy a great family member.
Be open to new people, they may come in an completely mess you up, but they may come in and completely amaze you. Isn't it worth the risk?