You hear this all the time, but it's true: focus on changing your lifestyle. Yes, you're doing this once again (as most of us have), but this time it's going to work because you're going to change your thinking about weight loss:
-Don't worry about how long it takes to get to goal. You'll get there when you get there. We all lose weight in different ways, so don't compare your loss to your friend's (or to that in a previous attempt). Just take it day by day and think LONG-TERM.
- Revel in your losses, but expect the periodic gain. Sometimes it's a gain for no good reason. Sometimes it's deserved. The key is to think long-term, dust yourself off and stick with the program. Learning this lesson will really help you in maintenance, too, because the process doesn't stop at goal but continues indefinitely. It's about minimizing the setbacks.
-Don't think of your last attempts at weight loss as failures. Instead, think of them as warm-ups for this final run. Think about what worked and what didn't work for you in past attempts and modify the WW plan to suit YOU. You don't have to follow the plan 100% to be effective. You do have to figure out how to make it suit you and your lifestyle. In my case, the WW points range was too low for me, so I ate more. I lost more slowly, but for me eating more on a daily basis was what I needed to do to stick it out to goal.
-Track your progress. Track weekly weight, monthly measurements, exercise stats and etc on a piece of paper. It can seem tedious, but it can also provide good inspiration when you're feeling unmotivated. I have a year's worth of data that I still from time to time pull out for motivation. When I find myself up 5 lbs, pulling out those old measurements and reminding myself that I used to have 47 inch hips really provides a good incentive to get back on track.
-Immerse yourself in good things about weight loss (and there are some). Read success stories, feel really smug and superior about how you can zip that pair of pants that you couldn't just a few weeks back, treat yourself to new fitness gear, try new foods/recipes and etc. Enjoy the process by focusing on what you can have through weight loss and not on the things you can't have. Conversely, remind yourself periodically how absolutely gross you felt being overweight (pulling out hideous snapshots as needed). Sometimes a negative shot of reality is just as motivating.
-I know you know this, but...If you don't do it already, figure out a way to love exercise. If you can't find a way to love it, at least learn to accept that it is a key to weight management and good health and something that just needs to be done.
I'm sure there's more to say, but I'll leave that to others. Best of luck to you. It's an achievable goal - just don't give up.