I overshare too. I try to be as honest as I can, not lying to myself or to others. That said we can't avoid white lies because of the so called "superego" (Freudian). For instance when someone asks us "How are you ?" and we respond "I'm fine thank you, How about you ?" even if we are depressed and deep down, we might don't really care about how the other is feeling. That's just one example of white lies that stems from a good intention but they are still lies i.e. not the truth of the matter.
I have some basic principles that I try to apply
1) Prime Directive (the Star Trek one)
3) "Don't do to others what you don't want them to do to you (variation on the same theme : "Treat others the way you want to be treated (i.e. kindly by default ).
4) (and that's from Bruce Lee) "Honestly express yourself !" hence the "not lying to myself" above but of course it's difficult to apply it in every aspects of life because well, Superego.
Note related but I also have a "security protocol" that I call DEFCON because I'm not a care bear.. .
Edit : This post was initially a quoted response but that post has been deleted so I modified it slightly (just a touch).