How to get detached from my ex?

I was in a relationship with my ex for 8 years. She was my 1st everything from being the 1st person i loved to the 1st person I had relations with. Now we haven’t been together since the beginning of the year but I haven’t been able to get over her. She has got a new friend and now I’m super jealous. To the point we’ve been getting in a argument all the time about this new person. We still live together but as housemates due to just helping each stay on our feet. So how can I be detached from her with being in the same household.
How to get detached from my ex?
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