Love your friend with some reserve, for he might become inimical to you someday.
Despise your enemy with some reserve, For he might become your friend someday.
~Ali (RadiAllahu Anhu)
When we get attached to people, we fail to realize that hearts change, and for some reason or another we will split ways from our friends. Similarly, those whom you look at in a negative light may be the one to save you and heal your pain. Have a open outlook, while preventing yourself from getting hurt.