I'm the same as River, I eat healthily Mon-Fri, I have smoothie, bran flakes and dried fruit for brekkie, salad / ryvita / wholemeal roll for lunch and a healthy meal in the evening, I only snack on fruit or nuts and drink loads of water. At the weekends I can have takeaway without feeling guilty although I do try to eat more fruit and veg at the weekend, I don't force myself! I might have something I like, like juice or a smoothie or fruit on a dessert or veg with my meal.
If you make little changes like having a glass of juice (make sure it is 'real' juice and not those Sunny D types) first thing in the morning then you have alreday nailed a fruit portion before leaving the house, if you then throw a handful of dried fruit, or berries or chop a banana on some cereal you have two portions by breakfast time!
I also exercise three times during the week, but again I don't make a point of going to the gym or classes or pool at the weekend, but I will walk wherever possible.
Ultimately though, only you can start making changes about what you buy when you go into a shop!