something always seems to get in the way

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This year I was sure I could start a healthy lifestyle and maintain it.. a couple of years ago (2009/10) i lost almost 25kg (which was a little much for how much I started off as) but restricting my calories wayyyy down and exercising a little over an hour a day. Obviously I put it all back on, and then some, around a year later. It makes me feel like such an idiot to think that if I had, at the same time, just started eating healthily and exercising moderately I would be that same size now, only a lot healthier and a lot happier. Its embarrassing to know that people see me as someone who's "let themself go" compared to how thin I was then when I could have avoided yo-yoing at all.

Since the beginning of 2011 I have tried to lose weight PROPERLY, slowly and healthily. Even getting down to the weight I started off as before I started idiotically almost starving myself would be progress. But I consistently have problems easing into it as a LIFESTYLE -- I will cook fresh (and may I add yummy!) meals (1350-1650 calories a day) and work out around four to five times a week.. Everything will be going great. And then inevitably something pops up which I use as an excuse to stop for a week or two.. Exams, work, somebody close will have a birthday that even though I've said I'll quit drinking for a while will use as an excuse to binge drink at.. Nobody in my life is in the same position of wanting to lose any weight or get any fitter, and the few friends that were gave up soon after new years. My family are all highly overweight but resist any offer of buddy systems or working out together.. they have even lower motivation than I do!! :(
I've lost almost 2kg since I started myfitnesspal (around december last year) but this fluctuates and is at a stand still. As you can see I have not filled in my diary properly for over a week.

I'm starting again today but I wondered -- Do you guys have the same problem with consistency, and if so how did you manage to push past it? I WANT to be and feel healthier and fitter, and obviously smaller, but then the hungover sunday will inevitably come where I sigh and resign myself to a day of "acceptance" which will last a little while. Help!!!!!!!!!

p.s sorry for the rantily long post!