Sincerity

Recently I find that my answers on Quora can be so long, that I might as well have written them as a blog post...

So I figured, why not just copy/paste them into my blog.

I answered the following question on Quora:

How can I have someone be sincere with me?

I have a hard time feeling that people are being genuine with me, given my well-renowned position and reputation. When I am surrounded by my closest consorts, I still I tend to have this feeling in the back of my mind that people are only acting the way they do to gain favor even though I know they care for me deeply, and it's eating me alive.

My Answer:

Tempted to start with "this is not the right questions. The right question is..."

But I won't. In Quora, you should either what a person asks, or not answer at all :)

So my answer to the question is "you can't". It's actually quite simple - YOU can't have someone be sincere with you. THEY need to be sincere with you, and you have little control over that. Except if you already know what they really think, in which case you don't really need to talk to them at all :)
But, trying to help you with what seems to be your struggle, I'm going to say this:

1) I think that your best way to tell if someone is sincere with you is by past experience. If they have always been sincere with you, then there's a good chance they'll be sincere this time around.

2) Number 1 brings out the question - so how can I tell if a new person is being sincere with me? Answer: you can't. Someone once told me that if con people were easy to spot, they'd be out of a job. I tend to keep this in the back of my mind.
I'm a lousy judge of character. I think most people are, especially the ones who think that they are good judges of character. This is, again, due to the fact that good liers are very experienced at misleading people. So the question I have in mind when a person I don't know tells me something is not "are they sincere", but more of "what's at stake here, if, god forbid, this person is not being honest".
I find this to be an excellent way to deal with people's sincerity question. It reduces the stress level resulting from this question that keeps popping up in your mind, and it actually creates a learning experience. If there's not too much at stake, you can assume that you don't know if the person is being sincere, and just wait to see whether they were or they weren't, and then learn from it a little.

3) Unless you are Barack Obama, The term "eating me alive" suggests that you may be taking this subject way too seriously. The guy at the store is giving you advice aimed at getting you to buy the product that gives him the best margin. Your dentist may be recommending expensive treatments that will help her redecorate her living room. Your boss may be giving you advice that is not only for your own good, but also for his own good. Your employees are doing good work not only because they love you, but also because they want your job one day.
It's OK. You have to learn to live with it. Respect everyone and suspect everyone, but don't be un-trusting. Don't be naive, but be a sucker sometimes, (knowingly, even). Getting screwed, when the price isn't too high, is a very valuable learning experience.
Make sure you are bothered by what's important