When I started my career in education, a colleague told me about a student who was usually very well behaved. With one seemingly inexplicable exception: whenever this teacher would speak in generalizations, the student would, without raising his hand, blurt out how one should never make generalizations and that generalizations are the root of all evil. The child would continue to work himself into a frenzy and basically become hysterical.
When it came time for parent-teachers conferences, my colleague thought he would raise the issue with the child's father. He explained that there was something he didn't understand: "Every time I make the slightest generalization, your son becomes hysterical." The father's eyes immediately bulged out, his face reddened and he responded at the top of his lungs: Rabbi every time!?!, you mean to tell me he does this every single time?!?
Because our children learn the most by our example, we may find out that we are not always transmitting the messages we think we are. To give a common example, we may tell our children how important it is to be honest and even scold them severely if we catch them in a lie. Although we may sincerely believe that we are honest people, our commitment to truth may not be as solid as we think. This sometimes becomes apparent when a child at home answers the phone and tells us that someone we don't want to talk to is on the line. How many people have never uttered the words, "Tell them I'm not here"? This, right in front of the child you just scolded for lying. The child will immediately conclude that truth is not really important for mature people and that it is only for children. When there is a conflict between what we say to do and what we actually do, the child will almost always favor what he has seen actually practiced. (Incidentally, the Talmud seems to agree with the logic of the child by generally finding the action of a sage more authoritative than his words.)
Speaking on the phone happens to be an Achilles' heal for many of us, as we often forget that we are having a private conversation in public, or at least in the presence of whoever happens to be within earshot, -- and the advent of cell phones has made this even more embarrassing. One hears people in the middle of the street carrying on all sorts of conversations as if no one could hear them. The telephone transports us, as it were, into the presence of the person to whom we are speaking and away from where we actually are, and therefore brings down our guard. As a result, our children may hear us gossiping, cursing, lying and who knows what else in our casual conversations with friends. Ideally, we need to work on these shortcomings simply because they are shortcomings, but in the meantime let's at least be aware of our children listening (sometimes quite intently). Realizing that children pick up what they hear us saying on the phone can and should motivate us to only say things we would want our children to hear.
Even regardless of our impact on children, greater awareness of who is in front of us can help us become generally better people. In Tehillim, we read the famous statement, "Shiviti Hashem lenegdi tamid" - I will place Hashem in front of me always. G-d doesn't need us to put Him there - he is always in front of us, whether we like it or not. What David Hamelekh is saying is that it behooves us to be aware of G-d's presence constantly and that such an awareness is usually enough to prevent us from doing the wrong thing. In general, we need to realize that G-d is just as much in front of us in our most private moments, as our children are in front of us when we are making a phone call.
In truth, most of us are more likely to control ourselves because of our actions' impact on other people than out of an awareness of G-d; no less a figure than R.Yochanan ben Zakai told his students that they should strive to have as much fear of G-d as fear of their fellow man. When his students expressed surprise at his seemingly low expectations of them, they protested, to which Rav Yochanan ben Zakai responded "Chalavai!", meaning would it only be that you could reach that level, it would be a very unusual and impressive feat.
No matter how insignificant man is compared to G-d, we are usually more affected by others' visible reaction to our deeds than by G-d's less immediately perceivable reaction. Consequently, there are people who actually reevaluate their lifestyle when they start having children. This is really a very rational reaction, when we realize the great power we have over shaping another human being, a human being that we love so much.
In one of his most brilliant essays, "Ben Sorer u'Moreh"* (Collected Writings, vol. VII), Rabbi Samson R. Hirsch addresses the tricky theological problem of G-d's punishing children for the sins of their parents. He points out that the Torah is simply presenting empirical consequences of poor behavior. In other words, just as a polluted atmosphere has measurable negative impact on our bodies, a polluted parental environment has measurable negative impact on our children. Similarly, whenever the Torah warns of consequences to moral depravity, it doesn't mean that G-d will decide to punish us in His anger. Rather, it is saying that all actions have natural, albeit not always immediately apparent, consequences. The Torah thus posits that all vice, no matter how small, will lead to some level of self-destruction in the long run.
We need to understand that when we go down, we take others down with us, usually the people we least want to hurt. Our moral behavior is not just a personal question; it is just as much a decision regarding family and communal responsibility. As such, we must not only worry about our own fate, we must also consider the fate of our children.
*A Ben Sorer u'Moreh is often translated as a wayward child. He is a child who is completely delinquent in his behavior towards his parents and thus seen to be irredeemable. One opinion in the Talmud is that Ben Sorer uMoreh is only a theoretical construct and that there has never been such a thing as an irredeemable child.