Think about it. How many new people do you meet every week? One? Ten? Hundred? Depending upon the nature of your vocation or occupation, you may be meeting anywhere from five to five hundred people everyday. You forget the faces, but some impressions remain. Do these people influence you?
In the poem Ulysses, Alfred Lord Tennyson said, "I am a part of all that I have met." This implies that we are constantly reshaping our personality on the basis of our experiences. Some experiences are strong enough to leave a deep impression. The ones that are insignificant affect us on a subconscious level and leave subtle impressions.
Hence it becomes imperative that we surround ourselves with people who are likely to leave a positive impact on our psyche. No negative minded, good-for-nothing people, but caring friends who will help us find eternal love and happiness.