Hi OP,
I've been on a diet for 74 days now and I'm loving it. Like you, I've never been able to stick at one for very long at all. My record before this diet was 22 days.
For me, there are a few things that have made this diet different:
(i) Frame of mind. This time I was absolutely ready to lose weight. Previously I'd thought "well I could do with shedding few pounds but it's not that bad" or "meh, life's too short". This time I was 100% ready and determined to do it because I was just fed up of looking and feeling like shit.
(ii) Clear time. I started just over 70 days ago when I had a very clear stretch of time to do the diet with no interruptions or distractions. There were no big birthdays, Easter, Christmases or holidays coming up so it was an ideal time.
(iii) Cutting reliance on food and drink. Me and DH used to have a curry every Saturday night with a bottle of wine each and a few shots. That was what weekends were all about for us. It was hard at first but we just brutally out a stop to that and haven't had a drop of drink for 74 days. It was hard the first couple of weekends as our whole routine had to be changed but we just replaced the take away curry with low-calorie buffets or homemade vegetable curry and replaced the wine with non-alcoholic cocktails- loads on Pinterest. So it still feels like we're having a Saturday night but we're not having the calories and we don't wake up with a stonking hangover. My Sundays are amazing now because I'm not spending all day with a thick head.
(iv) Only calorie counting. I don't take account of things like saturated fats etc., I only go on caloires. I know lots of people will say this is stupid but from a purely weight loss perspective, this works fine.My rule is that across a week I have to be 3,500 calories below my RDA so I'm not necessarily calorie counting everyday but adding it up across a week. This gives more flexibility for having a little something extra on the weekend as you can mkae it up in the week.
(v) No foods are banned. Related to that, because I'm only calorie counting, I can eat anything I like as long as I'm not over my calorie allowance for the week. For my lunch today, I've had tea and biscuits
but it's only come to 400 calories so that's fine. This means that when I need chocolate or I'm craving some crisps, I'm perfectly allowed to have them as long as I add the calories to my count.
(vi) Exercise every day. I've made myself exercise every day. Some times this isn't possible but the rule is no two consecutive days without some form of exercise. I try and swim three times a week with arm weights on and then I also do free weights at home every day when possible. I've really noticed how much healthier I feel for this and I can see some definition coming in my arms! I also think (no evidence though!) that exercise speeds up your metabolism.
(vii) No weighing yourself. I weighted myself at the very start of the diet just to see where I was. I won't weigh myself until the end of 100 days. I'm goin by what I look like and how I feel rather than some arbitrary measure of weight. Women's weight can fluctuate massively so I don't think it's a very good indication anyway and I find it very demotivating.
(viii) Set days rather than weight. Related to that point, I have set myself a diet of 100 days rather than a predefined weight I want to get to. I find this much easier to manage as I'm not thinking things like "I should be 2lbs lighter by now" or "more should have come off by now". I'm just going with this for 100 days