Never accept anything as truth if there's no solid proof behind it. Be willing to say, "That's a very pretty idea, and I like it, and I can provisionally accept it as a nice idea pending further data."
Go back over your old influences, to find out where your ideas came from. Watch it, read it, record what you're taking in. Each new reading, each time you re-input the input that you took when you weren't aware of it, you become more aware of the things you didn't know you thought all along. And then you can ask yourself if, really, a sitcom about a dysfunctional family was the best place to pick up the Rules of Interaction between mates. Watch and read all the trash you want, but keep track of it so you can use it to debug later.
Personality has never been a static thing. It's why listening to yourself on tape from some years ago often has the power to be embarrassing. I blush to read my journals from when I was ten. If I'd known then what I know now, I probably would have phrased myself less tritely, but hell, I was ten, you have to go through ten to get to twenty.
Always remember that some of the input you get, the input that you base your other personality decisions on, could be flawed. Maybe the book is wrong. Maybe the person you've taken as a role model is a really shitty role model. Most of this you won't realize at the time. Keep a log of who gives you which examples, of what characters in your entertainment you like, and why, and which ones you hate, and why. What embarrasses you? What pisses you off?
Always go back and re-examine. You aren't competing with someone else, someone you don't know. You're competing with yourself, bootstrapping, seeing if you can't be a more effective bastard than you were last year, for whatever "effective" means to you. Pick out the stuff you like about yourself and celebrate it. Pick out times when you've been a role model that you want to emulate. Figure out how you'd feel about someone else like you doing the same, and see how well they match up. Figure out in whose company you're a person you hate, and avoid them. Figure out in whose company you're a person you like, or could get to like.
If you take something on faith, be aware you're doing so. I would say, never take anything on faith, but that isn't the human way of things. So be aware of it. Consider the risks of taking this thing on faith, and the risks of not doing so. If you take it, and it turns out not to be the case, what will be the effect? If you take it, and it turns out to be correct, what will be the effect? If you don't take it, and it turns out not to be the case, what will be the effect? If you don't take it, and it turns out to be the case, what will be the effect?
Where the Vulcans go wrong is leaving emotions out of it. Emotions are part of what makes us human. Compare all cases, with and without emotion.