OK so... I've been hovering around 127-130lbs for the past few months. I was doing great losing weight steadily - until I went on holiday

By some miracle I only gained about 3lb which I thankfully lost soon after I got back home. But I haven't been able to keep my diet going consistently since! I either go into maintenence mode because it's 'easy' or get back on the dieting wagon for about a week or so - then have a couple of really bad junk food or carb-filled days and am back to square 1 again, having just gained back all the weight I lost that week!
I have pretty much been gaining and losing the same 3lbs over and over again since
August! Yes, I know it's a good thing I have at least managed to stay at a steady weght rather than gain it back, but... I am sooo frustrated with myself!

I just want to hit my next mini-goal of 125lbs already and I am so annoyed that I have lost my discipline! Have any of you had this problem? How do you get back into the swing of things?