The main point with truthfullness as with the other precepts is to cultivate some sort of peace with the world. You let the world rest and slowly the world starts letting you rest in return, and your mind can stop thinking 'Why didn't I tell him ....? Next time!'. And morals do not only balance your mind, they're also essential for good physical health. Violent persons will always have a tensed body as they percieve so much violence and hostility around them. So without living well, you can't relax. At least I can't.
And it feels good on its own, this training in morality, at least that's my experience. I can't really meditate yet, and to be honest, I'm trying to find a teacher, but I'd also love to have someone teaching me about morals, life and especially the right attitude again like when I got my first "training" far away in India in Yoga.
When hurting others, we are not aware in this moment and we solidify the illusion of being a seperate being which we try to shatter with our practice, so it is quite obviously counterproductive when we practice at home and fight egoistic wars when out of the house. But true, it's difficult to change habits. But at least lying and hurting is just that: a habit, not your character. Best is changing your attitudes, then the habits follow.
