We make promises easily. Often, the heavy weight is converted into the force that takes them to the end.
One interesting example that I have learned lately from communication course: A person sometimes unconsciously take one-way communication model (monologue model), which leads to the blame on the transmission of information. Content (information) matters. Think about this: when we yell at each other (the same content) does not necessarily make the receiver understand better. He/ she still disagrees with you. Interesting example, really (communication course is interesting).
Try to keep your promises a little bit longer.