How do I not get derailed?

My best recommendation for staying on track would be to make that track as easy and smooth as you can possibly make it.

Yes, in order to lose weight, habits need to change. But it doesn't necessarily need to be extreme, immediate, total change; nor does it have to be precisely perfect every single minute of every day.

Better than before: That can work.
Pretty good on average, most of the time: That can work.

I don't know whether this applies to you, but it seems like quite a few people arrive here thinking they need to do some extreme, restrictive named diet; eat only "good" "healthy" or "diet" foods; omit all junk food, treats, fast food, or any other type of food they think is "bad". On top of that, many seem to add some intense new exercise program that's unpleasant or even punitive.

That kind of thing is hard to keep up, and none of it is essential. Eating somewhat less (in calorie terms) is essential (but counting the calories isn't the only way to achieve that). Getting somewhat more activity (daily life stuff or formal exercise) is helpful, but completely optional for weight loss.

I don't know about you, but I can't keep up white-knuckled willpower, motivation or discipline forever . . . and forever is how long I'd ideally like to stay at a healthy weight (especially now that I've figured out how good that feels). That puts a premium on finding new, reasonably easy, ideally enjoyable (at least tolerable/practical) new routine habits . . . habits that can run almost on autopilot once discovered and practiced for a while.

It's those routine things we do the overwhelming majority of our humdrum days that matter the most. That one day when we eat too much cake, or work out for 5 hours? A drop in the ocean. The daily routine is the ocean. Focus there, I'd suggest.

We each have different preferences, strengths, challenges and lifestyles. That implies to me that we will need personalized tactics that take all of that into account. Other people can give us ideas to try, but we have to find the right personal solution(s).

One day, one meal off track: Doesn't matter. Just return to healthy routine. Even a whoooole vacation of (say) 2 weeks out of 52 weeks is a minor influence. Just return to healthy routine. Only giving up altogether fails. Trying something that doesn't work is a learning experience, not a failure.

You, @Floydo2014, report gaining around 15 pounds in a couple of years. Gaining 15 pounds in 2 years implies having eating on average roughly a mere 72 calories more daily than a person has burned on average. Seventy two calories. Less than a tablespoon of peanut butter. A tiny bit extra of ranch dressing. Or, maybe not a small thing daily, but the big ol' fried cheesy thing with drinks every other weekend. It doesn't take much for weight to creep on.

The implication is that we can harness that same idea in reverse. You probably don't want to wait 2 years to drop 15 pounds (though that's feasible). Eat 250 calories fewer than you burn, eating whatever you choose and doing whatever you do, lose half a pound a week approximately, be most of that 15 pounds down by around the end of the year, with minimal pain required.

Or go a little faster (not much faster, I'd suggest, if only 15 is the total you need to lose). But learn new habits along the way, habits you can stick with long term so you don't find yourself here again with the same issue in a year or two.

Just my suggestion. It won't be the right approach for everyone - no one thing is. But you asked for tips. I was overweight to obese for around 30 years. I found a way - wish I knew how to sell it! - to flip the switch in my head to "committed". In a bit under a year, I'd reached a healthy weight, and I've been at a healthy weight for around 8 years since. The quality of life benefits have been huge, for me. I want that for everyone, however they personally need to get there.

Best wishes!