Where a lot of self-improvement initiatives seem to falter --
Failure to consolidate the gains.
After any period of self-development -- whether that's in health, productivity, attitude, or a particular skill -- there will be a time when you've got a loose collection of new habits that aren't fully happening all the time.
Inevitably, eventually you get caught up in being busy, or get ill, or whatever, and many of the new gains fall over like a house of cards.
It's worth keeping this in mind when trying to make positive changes. From time to time, you need to consolidate the gains.
Ideally, your new practices are written down. I do a mix of writing them on paper, tacking sticky notes to a whiteboard and gigantic piece of cardboard right above my desk, and keeping them in digital files like Google Docs.
If you haven't written down any of your particular rules and reasons for keeping them up, you want to do that as soon as they look shaky at all. That way, you have a reference to go back to if you start to fall off.
When you do start to fall off (and this happens to almost everyone), it's time to slow down a little on building new improvements and consolidate what you've got. That means reviewing what you've written, your reasoning, and looking to restart what you've left off.
If you've fallen off due to external circumstance, it can make a lot of sense to put a hard cutoff date for restarting. If you're traveling and off your desired diet, you can make something like, "As soon as the plane lands, I'm back on it." It works pretty well.
Having habits almost fall off and then get re-booted seems to be a big part of the process of gaining new habits, and a part of it that most people aren't prepared for.
But similar to how spaced repetition helps with mentally retaining information, having new habits start to fade and then consolidating them does wonders for building them up stronger.
Plan for it, love it, and go for it. Many improvement campaigns start to falter. By being prepared for it, writing down your procedures and reasons for doing something, and reviewing it when it starts to get shaky and doubling back down, you wind up keep the best of your habits built into your life, and making tremendous progress.