Are you considering divorce or breakup, but deeply care about the other person?
I have been in two marriages where both parties were going in such different directions that one of us decided that divorce was the only way to move forward.
Breaking up is a rather painful process for both parties no matter who initiated the decision for whatever their reasons were.
If you are divorcing your best or only friend, it can be particularly daunting. Do what you can to ensure that you have your own friends, and preferably keep close with mutual friends to ease your troubled mind.
Some things you can do to make things easier for both of you is to find a way to express that such a situation is unpleasant for both parties. It is actually possible to lean on each other during this transition! If you are your only friends, it is okay to go get coffee at your mutual favorite place. You might be on your phones or reading different parts of the newspaper the whole time, but this being present for each other is still beneficial.
In my first marriage, I was not the one to bring up divorce. But I understood where he was coming from. If we weren't romantically happy with each other, we should be available to find that happiness elsewhere.
Ultimately you should be finding genuine happiness within yourself, rather than depending upon external circumstances or another person to "make" you happy, or to "complete" you.
But if you find yourself in an unhappy relationship, and you have made attempts to make it work, but it still isn't, then maybe you need to set yourself free (or set the other person free).
Consider how your relationship will evolve if you stay in it. Are you or the other person heading for unfaithfulness? If so, have you considered opening up the marriage so that whoever needs it is free to enjoy the company of others?
In my first marriage I had a higher libido than my husband. In my second marriage my husband had the higher libido.
In the first marriage, he just needed to know I didn't actually care about the guys I was with, but the minute I expressed liking a guy, that was when he called it a failed marriage.
In the second marriage, I struggled with my territorial jealousy, but I couldn't keep up with my husband, so I opened up the possibility for him to be with others.
We had discussed the open marriage theory a few times before I blatantly said that I didn't care if he had sex with another woman.
He's a handsome guy with an adorable quirky side. I knew by that point that a handful of women had made themselves available for him. One of whom being half his age and cute as hell. She was very open and honest with me about her attraction for him. I was understanding.
Another aspect to consider in your decision-making is the level of abuse taking place. This isn't limited to physical abuse. Mental and verbal abuse run rampant. People are so used to the way they grew up, that they don't know what a healthy relationship ought to look like.
Dysfunctional relationships can be difficult to spot when you are in them, and getting out of them can prove tricky.
You became attached to this person for a reason, and that reason may still be there, and maybe even other reasons to stick together came into the picture.
You have a history with this person, your relationship may have been intoxicating and may still be so! But if it is toxic, you need out. Having numerous wonderful moments, doesn't mean that marital bliss is in your future with this friend.
Divorce or breakup doesn't necessarily mean the end of the friendship either. However, that is completely dependent on the individuals being able to bridge that psychological gap and whether the relationship is an abusive one that requires more distance.
Life is short, and divorce is pretty gruesome, but it may be the fastest route to overall happiness for both parties, opening the way for a completely new future as yet unknown.