One thing at a time
I've said this stuff before. What I haven't said, and should have, is that yes, it's hard, and that there's a million little accomplishments that add up to the "finished product" of a changed body and a new lifestyle, but that the fact that it's made up of all those little accomplishments means that you really don't have to do this all at once.
I've compared it to mountainclimbing (with the exception being that when people say they want to climb Mt. Everest, the response isn't "THANK GOD, I was wondering if you were ever going to get around to it!"). Which is correct, in a way, but I have a few other ways to describe it.
Starting a weight loss program, particularly one in which you're handed a Plan all worked out for you, feels similar to being a juggler who has been working with a comfortable number of items and suddenly has twenty new items thrown in at the same time. Some are brilliant enough to manage to catch them all and work them all into the already ongoing juggling routine immediately; most will try desperately, catch some, drop others, and occasionally lose everything, including the items they had under control in the first place.
Jugglers are wise: even when they're adding a lot of items in a short period of time, they still add only as much as they can handle at that moment, wait until things have adjusted, and then move on to adding more. It strikes me as a very valid way of doing things. Add a few new things, and adjust. It's not just your body that needs time to adjust-- so does your mind, and your schedule, and your family. Drastic action is much more likely to be rejected than slowly adding new routines and new actions in small quantities. Start small, start few; add more things, and work the small things up to larger things.
I've got another analogy which I've used on several folks lately. The process of getting all these habits built is not unlike hauling a giant trunkload of groceries from car to kitchen. Yes, there are occasionally people who are gifted with long arms, vast strength, superior balance, a miraculous lack of obstacles in their path, and an ungodly amount of luck, and who manage to pick up every single damn one of the bags and haul them all to the kitchen at once and without incident. I don't personally know any of those people. Bags rip, garden hoses have been left bunched up on an innocent stretch of walkway, gravity causes avalanches within the bags that cause them to shift, causing me to grab at them, causing me to lose my grip on something else, causing a frantic and highly comic juggling routine that almost always results in a total loss of grocery/bag cohesion, groceries scattered on the ground, and me sitting on my ass cursing up a storm.
What you do instead, if you're setting yourself up for success, is to make a lot of trips, taking what you can handle on each trip. It doesn't help that some of these are insanely overpacked bags (there is ALWAYS some kind of smartass who will put all my canned goods in a single bag) and have to be hauled one at a time-- hell, sometimes a particularly bastardly bag is too heavy to haul all by itself and must be taken in pieces, a few items at a time.
It's the whole "baby steps" idea. I think of it more as a way to practice success. When you're used to trying to do it all at once, and failing, it's hard to trust yourself on any one of those things. If you just get one new habit in place at a time, though, then you're more likely to succeed since it has your full attention, and you can then build on that feeling of accomplishment and pride to pick up another new habit, and add that to the plan. One at a time.
It might be the different mindset between "diet" and "lifestyle" that's the trip-up here-- because yes, you can line up a huge number of things that you will grit your teeth, power through and endure for as long as you can take it, just in the name of losing weight. You can do that. But the thing about that approach is that when you're enduring something, you're setting yourself up to fall down simply in search of relief. When you're taking these baby steps and making them a part of your life, one by one, there's this period of examination, of adjustment, of wiggling around to get comfortable in this new thing-- then settling in and having it as part of your life. In that case, when there's stress and horrible things happening in your life, you're not so likely to drop the new thing, because it's not an extra stressor, it's just part of your life.
You do not have to do this all at once. You don't. Yes, a lot of the aspects of healthy living compliment each other and there's a sort of epic grace and beauty to it that sometimes I find myself staring at and saying, "Whoa!"... but you know, they're lovely on their own, and you'll get to the other parts eventually. You slowly build up these talents, like you're building muscles in your brain.
Ease in. Get used to it. Incorporate things one at a time. You don't have to fear this stuff, because you don't have to do it all now-- you just have to start on one thing. One small thing. Everything else will come from there, I promise.