When you make a promise to your spouse or say you will do something for your spouse or family and then you don't keep your word, you are letting your spouse down and hurting your marriage. (Google)
Keeping your word and following through on your promises helps to reinforce the trust that your spouse has in you. Not keeping your word tells your spouse that you simply don't care. (Google)
(A headline) McCain to Obama: Keep Your Word to the American People. (Google)