I have just started my second 12 week challenge. Did one at the start of the year and lost 7kg. Took a month off and put on a couple, now back on to shift a bit more. 12 weeks is a good goal time for me and my goal is to lose 6kg in that time. I have changed my ticker so it reflects the start of this one not the last one as I know that it is non-negotiable to go above my current starting weight. I have a bit of a longer goal - down to 65kg by my birthday in March next year. I weighed in last week at 76kg and at the start of my first 12 week challenge just after xmas last year was 84kg.
My best motivators were to find diet goals that were easy to implement - I cut out buying junk food for work because I would eat whole packets of biscuits in one afternoon - and go a bit easier on the other stuff (eg. saying no takeaway is not realistic for me). My best exercise tip is to find a team sport that you like. I love indoor soccer and now play twice a week and practice on my own, I also ride my bike to work to cut down my environmental impact. I defintely can't see myself going back to the weight I was.

So good luck for your journey! You deserve to succeed in this because having a healthy body will allow you to do so much more. One of the most motivating things I have heard for weight loss (from Lucy I think) is that time will keep ticking by whether you lose weight or not. Xmas and birthdays will come around again and it is your choice to be the same as you are now or a lighter version. So even if it happens slower than you expect, the only thing you need to worry about is to keep up your end of the bargain and time will do its part too.

Good luck!