One of the characteristics of a good partner is being true to his word and keeps his promises. Will you have it any other way? If he keeps breaking promises without remorse, then you'll start simply not believing what he says. You'll always expect the worst.

There are people who break promises and know well enough to apologize and/or make up for it. There are those who break promises and act as if they didn't do anything wrong. Then there are those who break promises and promises not to break promises again. There are even those who break promises and act as if it's your fault when they break their promises.

When you've got promises broken, trust is broken as well. You expect better from your partner and when it doesn't happen, disappointment sets in.

It goes without saying that if you expect your partner to be true to his word, you should be true to your word as well. Otherwise, what's the point?