I looked in the mirror and lifted my t-shirt, noticed my belly was starting to get fat.
Then I quit sugar and carbs and never went back - but it was hard, after 2-3 months I got crazy cravings for carbs but I pushed through it, I compare the pain of changing something important to the most "extreme alternative" - which in this case and in many cases around bad habits is death.
I do eat some carbs but not much, I'm 100% off bread and sugar and processed foods and honestly I think that in itself is enough to make a massive difference, you don't need to cut out carbs entirely.
I feel much better, my energy is even throughout the day / evening, I used to get tiredness that came on suddenly a lot but that's gone now and I used to get frequent headaches and they've gone too.