I "only" had around 30 pounds to lose but I have been trying unsuccessfully for 6-8 years. I tended to get depressed about "letting myself go," get overwhelmed by all I had to do and then sit on the couch and binge-eat, wondering why I couldn't get myself together.
A couple of things that helped me this time for sure are:
Check out
The Beck Diet Solution by Judith Beck. I found out about it from this forum, I took out a copy from the library and ended up buying it. It has behavioral strategies that work with any diet, so even if you only add a couple of them, it really helps. One thing she recommends is losing weight in FIVE pound intervals.
The other thing I did that finally worked is I
committed to a plan for a certain number of months (for me was four). That takes the away the constant second-guessing, anxiety about not losing quickly enough, etc. At the end of that time frame, I am going to re-evaluate and decide if I want to continue, switch strategies or move to maintenance at whatever weight I am at that time. I may have to decide that a higher weight than I used to be is FINE. I don't want to live the whole rest of my life trying to lose 10/15/20 pounds.
A third thing I did was focus on diet first. I know without a doubt that exercise is important and that is the next challenge that I will undertake but
for me, it was too much to tackle it all at once. I tended to get overwhelmed and give up. Also, with reference to the previous point, when I start exercising for real, a higher weight may end up being just fine. I am now only about halfway through my weight loss but I would be OK at this weight if I tone up. So that's my next step!
All that being said, I think walking and some stretching/gentle yoga should be non-negotiable and part of daily life. Of course I am terrible about actually doing that.
Best of luck to you, and hopefully some of our suggestions will help
PS I forgot what completely turned things around for me this year. I found a copy of
8 Minutes in the Morning by Jorge Cruz. It has daily readings and 2 simple exercises (plus warmup and stretches) that supposedly take 8 minutes. Totally cheesy, but what worked is it got me jumpstarted on taking a few minutes every morning to think about the plan for my day. I highly recommend setting an alarm for a certain time in the morning (mine was while having coffee) to plan the day... I don't do the simple exercises any more but that planning and daily recommitment helped me immensely to get on track.