Henry Ford is quoted as saying, "It's not what you say or how you say it, it's how often you say it". While Ford referred to advertising, his point applies to all kinds of communication. Consistency reinforces your message.
Especially in our crazy-busy world - don't assume that because you told someone something once, they got it. That's why as a speaker, I make the same point in many different ways - and as a professional, a wife, a mother, a friend - I strive to cut people slack. People are busy and we all need to reinforce our points with repetition.
What we DON'T want to do is tell them once and build our case against them because they didn't get it.