I agree with Vicky - you've done it before, you can do it again. I know from my personal experience, when I was in my early 20s I had a very unhealthy lifestyle. I prioritized partying & most of my pay was spent on the weekends. I absolutely do not regret it - I had the time of my life!! Those days where I would not eat breaky & eat a cup of soup for lunch caught up with me though as I grew up & began eating significantly more, putting on close to 10kg, although I was not what you would call overweight. I recall going shopping and having to get size 12 jeans (imagine the horror! Omg haha). Well that was it. I came home, looked into diets and the next day I went on the soup diet and lost 10kg. I swore by it (the soup diet). I did it for 5 days at a time every time I put on a few kgs. I found it easy & it worked, as well as being packed full of veges & nutrition (unlike the shake diets which my friends swore by).
Anyway my point is, I think it's always harder the next time around. I wish for those days where I could eat vege soup for 5 days and drop a dress size, but it just doesn't work anymore.
Any loss is a loss no matter how small. Weight watchers taught me that - and even a no change in weight is still a win, as long as its not going up your are doing okay. Keep it up, you will get there!