Wow. Sea Girl, Fat Pants and Danni stole my thunder.
They gave fantastic advice, all of which I would echo whole-heartedly!
My major thing to get back on track is plan, plan, plan. KNOW what you're going to have for breakfast tomorrow, because then there's no option of getting something junky instead. If your stomach growls well before lunch, it's no biggie, because you KNOW that your allotted morning snack is _____, and you can eat that now. Planning totally saves me from all the bad last-minute choices I would make all day long if I hadn't thought things through!
And knowing you're at your lowest weight in 4 years CAN be a motivating factor... but sometimes I let it be an excuse to go off-plan a bit. Don't you let it. Decide that you're gonna be at your lowest weight in FIVE years... and work diligently towards that. You can do it, honey.