How do you make some understand that sticking by their word is IMPORTANT?

I don't understand how people can say they are going to do something, THEN DON'T!!!

Like "I'm going to workout today" then literally they're lying on their backs the whole day and makeup some excuse later like it's too late to workout. Or they are going to do something but then don't

How can you make someone see that their lack of integrity and living by their word is messing their OWN life up and also negatively effects the people in their lives also!

How do you make some understand that sticking by their word is IMPORTANT?
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