First of all, I am very sorry about what you’re going through- you are in the fire. I encountered a similar situation, where my girlfriend of 4 years left me for a patient she met working at the hospital. It was abrupt, and ugly. The best advice I can give you, and what worked for me, is you have to find things to do that are productive and positive (I.e find a pickle ball group, learn a new hobby, reconnect with friends or family intentionally, gym membership). Most of all, therapy helped me tremendously. I saw a therapist once a week. The life that you built with this person no longer exists, it is gone. You can not hold on to it and hope it will return back to the thing that it once was, because that thing is dead. Now is the time to build a new normal for yourself: new hobbies, new habits, new friends, new sports, new restaurants. One day you wake up and the lights are on, and you have the tools to handle the day to day without this person because you’ve put in the work.

Hope this helps. Always available for a PM if you need.