I remember when my son was born. I was mortified at the thought of raising him to be confident and polite. I mentioned this to my Allstate agent's wife in Irving, TX who replied, "Oh, that's the easy part." I was shocked she could so easily dismiss my distress, yet with two grown boys of her own, I assumed she knew a trick - she did, and I have found it to be some of the most useful advice I've ever received:
Live your life as an example to how you want them to live theirs.
Simplistic, and effective. Leading by example over the DO-AS-I-SAY-NOT-AS-I-DO of old returns real, actionable results. I couldn't be more pleased with the outcome.
It can be a struggle sometimes, to exude the behavior you want others to see when you aren't in the mood to do so, but imagining the catastrophic results of not doing so is usually fair motivation to continue. The wonderful part is how easy it becomes with just a little practice - always doing the right thing becomes an addictive game - leading you to always do the right thing. This is how the whole "mood" thing is overcome; it becomes habit. When your default action is to always do the right thing/behave the right way, its no longer dependent upon how you feel - and this reaches far past your children and becomes something everyone can see.