It is justified by experience and relations. You have a lot of friends and some of them are not like others. If you ask yourself that you could not be a friend to that person by looking his/her appearance. However, you know that it is a pleasure to know that person and you feel you are lucky to know that person. 

You reliase that your special friend have a very good heart and never betray you. You understand that your special friend has a very good heart and always be with you.