Harder or Harder

Does anyone else have an easy time starting things but a more difficult time once things are in full swing? I'm either being harder on myself or it's getting harder to do as well or a combination of both. It's not the first time that I start to lose weight and once I'm getting real results it's harder for me to push at it and continue to the end. However, it is the first time that I'm determined to push through regardless and I know I'll make it. I just don't understand why it's so easy for me to start things and get going on them and once they should be habits it gets hard. I mean, come on, it's been 6 months that I've changed my eating and exercise habits so why should it be so hard to get up and exercise now? Or why should my cravings be more now? Granted the cravings are different now because I don't crave bad foods so much as higher calories than where I should be at, but still it's driving me nuts.