What is it called when, "your word is your bond", goes overboard?

You are misunderstanding the concept.

It isn’t “going overboard”. it is a matter of whether you stick to your agreements. If you “change your mind” it means you cannot be relied upon.

If I agree to something verbally, my word is my bond. But if the other party finds a problem with the agreement, they can ask me to be relieved of the obligation without penalty.

The concept came out of stock and bond transactions done face to face. If I said, “I will pay $XXX for the September bond”, and you agree to the price, our word is our bond, our guarantee that we will exchange money for the bond. If I come back later and say, “I was supposed to buy the October, not the September” you may let me out of the deal if you choose. But your agreement to the original does not mean I also hold you to that original agreement.

@zenvelo I told my doctor that I was going to get a haircut, as my hair is bothering me. I changed my mind, and was considering buying ouchless scrunchies, instead.

It is the stuff like that bothers me from time to time. It seems overboard with stuff that cripples me. What is such a thing diagnosed as?

As I said before, you are missing the concept. Telling your doctor or your mother what your choice of hairstyle is, and why. is not an agreement.

The only time the maxim would apply is if you made an appointment with a barber and then skipped it. If that happened, you broke your word you would get your haircut, and you would owe the barber for the amount of money he is missing for not cutting your hair.

If the barber broke his side by closing the shop for the day, you would not owe him for the haircut, but he would also be considered unreliable so no one would ever make an appointment with him.

@zenvelo Ok. Thanks. I feel better now.

It is called “the start of World War 1”.
When the defensive pacts between all the countries forced them into the war.

Bond? James Bond.

Depends on the person / occupation. Politicians (any party, any level) cannot be trusted in any way. So their word is never their bond and cannot be trusted.

Next least trustworthy are clergy of all religions. Their reason to exist is to pass along lies and tell stories.

But the basic problem (to quote the famous fictional doctor Gregory House:) is that “Everybody lies”

So no one’s word is actually immutably honest and bondable. Yours, mine, the neighbor next door. So you need to live as if most people are not telling you the truth. You will be less disappointed in the long run.