Instead of being romantic lovers, they often feel more like roommates or siblings.
Therefore, if one leaves the bonds, the marriage is over, no matter how much the remaining spouse wants their marriage to continue.
So, imagining it as real— seriously, this husband of yours has provided 100% financial support for you for 40 years details are missing here in the letter , and you are still complaining? Both of you are just existing.
You may think of hiding your feelings and compromising for the sake of your marriage, but for how long can you put up the façade? You have some work to do if the marriage is going to be saved.