As well as what Happier said some things I found helpful was meal planning, but I only do the main meals. Breakfast is usually toast and eggs or porridge, and lunch is sandwiches, salads, soups or leftovers. I plan and shop for 7 main meals, and then try to make 10 meals by doing things that are made from store cupboard items or bits and bobs. Things like pasta with tomato and vegetable sauce, mac and cheese, homemade pizza or omelettes. Doing this means I can sometimes get away with 3 shopping trips a month rather than 4, or even 5 on a 31 day month like May was.
Another thing I do is cook double of things like spag bol sauce or casserole, this way I'm more likely to have something quick to defrost on days I don't want to cook, it helps prevent the takeaway temptation. Not completely, but it helps.
I rarely have a coffee out, or buy food out, but sometimes I still do this and have other small treats. I find that it's easy to become so bogged down with saving money and this makes me resentful. I start thinking 'Sod it all, what's the bloody point, I'm really miserable.' and go on an Amazon spree.
For me its like an over strict diet, I start out ok, but then break out and eat my own weight in jaffa cakes because I'm feeling deprived.