Lot of people had to learn the hard way of a lesson I taught my 3 kids (all 20-somethings now).

This simple lesson I taught them when they began High School: Just because someone talks to you daily does not make them your friend, it makes them an acquaintance. You will have many acquaintances throughout life, but only as many true friends as you can count on one hand. A friend will never stab you in the back, talk shit about you, and be there through thick and thin no matter what is going on with you, or their, lives at the time. Be friendly to people, but understand they are transitory. If you find someone who could be a true friend, cultivate that relationship and it'll last a lifetime.