How can I stop comparing myself with his ex?

I compare myself a lot with his ex like how he stopped smoking when he’s with her but he doesn’t even bother when he’s with me, how he cooked a lot for her but when with me he barely cooks and just orders, how he used to dress up everytime he went out but when with me he usually just wears usual clothes and slippers. What should i do?
How can I stop comparing myself with his ex?
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