How to eat clean and quit junk food?

I’m a very active guy. Play sports, gym, always moving.

I’ve always struggled with my diet since I was a teen. 23 now and at university, most days I can’t bothered cooking my meals. I end up buying takeout a few times a week.

It’s not as bad as it once was, but I really want to change. Especially my sugar intake.

I have poor willpower and mental strength and I was wondering how I get disciplined with my diet.

What worked for you?