Yet a stranger may only be being polite. They have no stake in your life. They could end up telling you how it really is...in their view. Or they might just say nothing at all. They become the sounding board you needed. No response required. Just quiet acceptance and postive regard.
And your friends and family may well love you no matter what. If they are true friends and genuine family in the holiest meaning of the term, they will be there for you. They, too, will be that mirror you need at times to see yourself how you actually are.
Bottom line, we have radar. We are able to find the ears we need when we need them. We just have to put aside our filters and see people as they really are. People reflect to us who we really are. What we like in them, we like or want to develop in ourselves. And just as true, what we do not like and perhaps are even repelled by in others, we do not like in ourselves. All we need to do is be mindful of this as we interact with others.
Strangers and friends are ends of the same spectrum. A stranger can be your best friend just when you need and a friend can be distant enough to share with you the objective truth. In the end, we need to look for the lesson in all our relationships because they all, casual or close, have something to teach us.