Breaking promises to our kids over time simply breaks the relationship. Our kids stop trusting us. Don’t take our promises seriously. To my knowledge, after certain point, there is no return.
Parents don’t break promises because they are bad parents, they break them because they don’t see how that little promise will cause an important effect in the future. The problem is parents forget all those that they had broke already. Our kids remember each one of them.
Learn to keep your promises to your kids, write them down, make sure your kid is clear on what you are offering. Ask him/her to explain the promise to you. Then honor them. Always!