I am sorry for the situation you are in. The cycling of emotions feels terrible. I am sure you have read different situations on this site and have seen the kind and knowledge people and their caring advice. A lot of advice will seem counterintuitive, and not what you want to hear. You are not alone, we know with what you struggle.
Feel free to post as often as you wish. Ask questions, journal, vent - it really does help.
Perhaps you can fill in some details. How long have you been married? Any kids? Ages of all parties?
You mentioned your W moved out to be on her own 7 months ago. Have you separated the finances, house payments, bills, rent of new place, is she just paying her way, custody of children (if there are any). I am sure you have made arrangements in these matters, I hope you will feel comfortable enough to share them. These are a source of attachment to your absent spouse, a method to hang on, probably unrealized and devious in how it continually ensnares you.
Other trapping thoughts are of her possible affair. You are correct, it will eat you up, grind you down, and an emotional breakdown is a real possibility. Good for you to see this hazard, and even better to reach out for help and guidance.
You state you know that her MLC is about her and that you cannot help her. It is clear you have done some homework and are leading with the correct foot, so to speak. You have heard, I am sure, focus on you.
You will hear this many times. It is very sound advice.
Focus on you.
You need emotional detachment. A place where the actions or emotional state of your W does not cause an uncontrollable change in your emotional state.
For me, accuracy was the key. I have wrote about it, heck who am I kidding I’ve wrote about all kinds of stuff.
Anyhow, be accurate in thought and heart - truly accurate. See what she is doing, what you are thinking, feeling, your behaviours, the effects at work. Shine that light on to your situation, into every dark recess, do not allow denial to hide out anywhere or gain a foothold. This is tough, too be sure.
As you look accurately, you start to understand. Undsrstnding will lead to accepting. Acceptance leads to detachment. More or less. This is not linear, and the delimitation between stages are not carved in stone.
In a larger view, you are addicted to your W. Don’t worry, I think that is normal, a good sign of a good relationship. However, now that very attachment is hurting you. Every time you act or behave like you used to, like your very instincts tell you too, you are reenforcing this addiction. It is a struggle to see this within one’s self. Once you do, you will realize that was the harder part, accurately seeing things helps with the withdrawal.
R678, I know I have giving you a lot at one time. You are 7 months in, I think you can handle it.
Focus on you.
DnJ
Feelings are fleeting. Be better, not bitter. Love the person, forgive the sin.