Promises have been there since time immemorial. Promises to remain together, promises to do something, promises to keep secrets, etc. Promises are deeply reassuring. They make you feel for that moment that things will be fine and nothing could possibly go wrong.
Some promises are done under oath, some with witnesses, some in sacred places, etc. From marriage vows to military oaths and all the smaller declarations in between, promises are meant to be honored. It's always better not to make a promise than to make one and break it.
Some people are better at keeping promises than others. They would rather do anything to the point of losing their lives rather than break a promise. They are very devoted and loyal to their promises which is commendable. Others on the other hand don't need much to break a promise.
For instance, someone may know how vital a secret is because they were told to promise not to tell anyone about it. They may even solemnly swear never to reveal it to anyone but they will still be unable to keep it to themselves. They break their promise by telling it to one person or anyone who cares to listen.
If someone entrusts you with a secret, it's always best to keep it. Likewise, if you make a promise, it's important that you keep it too. If you are unsure about being able to keep the promise, don't make it.
Many times effort is better than promise. Instead of promising to do something, just simply go ahead and do it. Because you can promise something that you are unable to fulfill later on.
Here is a hand-picked collection of promise quotes to bring to mind the importance of promises. After all, it's only fair to both parties to only make promises you intend to keep.