'I am Sincerely Fake'

Sincerely, SamHuang
How do you tell when someone is being sincere to you? Do you just have too look at the "sincerely" at the closure? Should people start stating "insincerely" when they don't mean it?

I am never know when someone is being sincere with me or its just a mannerly overly-used quote.

I hear "I miss you", "I'll be back", "let's hangout", "Nice to meet you", "I had a great time" daily. Are those people being sincere with me? my costumer who said they will be back never came back. My best friend saids she miss me, and in turn say to the other 200 people including strangers. Does she mean what she said.

Perhaps this is manner. Being polite require us not to be sincere and lie as much trying to make the other feel better.

I wish i can give you great tips on how to identify insincere people. But i can't. Because I am asking you this question to which obviously don't have the answer for. If I have have the answer and asking you trying to make you look smart and feel better that you have helped me, then i would be insincere.