Tooth Decay - Anxities around a filling (UK)

Hi,

So I'm in my early twenties and was told at my last dentist appointment there is tooth decay on one of my teeth after an X-Ray, and that eventually said tooth will have to be removed

I was told I can either have a preventative filling on said tooth, or do nothing - and that either way it'll have to be eventually removed

I have said yes to the filling (Getting it done later this month) but was wondering is there anything else I can do to prevent further decay since I'm worried on the decay worsening, etc.

This is the first filling I've had done as an adult, my oral hygiene could be better (Brushing only in evenings, flossing 2-3 times a week & a relatively high surgery diet), but yeah. I'm unsure if I'm over thinking it so any advice / just, knowledge on this would be appreciated :)