There is no crystal ball to predict that a particular friend will turn out to be a reliable, positive relationship in your life or, by contrast, that a negative association will cause you emotional distress, or worse. Since destructive or negative friends are not always that easy to spot, being forewarned is forearmed, as the saying goes. Some friends may be betrayers from the start; others may turn into betrayers because of what's going on in their lives or because of changes in their personality. Sometimes you need to consider what your friend is really like within the contexts of all the behaviors. I can't emphasize enough that you need to consider the root cause.

And in everyone's life, I reckon that it's part and parcel to have met some.

I should say that I have such honour to meet and get acquainted with them. HOW GREAT!