The meditation that I use currently is called Centering Prayer, which I've been doing (on and off) since 2018. However, my approach and process to it and with it has largely been informed by mental health experiences. I first encountered mindfulness meditation when I was doing Peer Support Specialist training for IPSTA (Iowa Peer Support Training Academy), as both a trainee and later a trainer. In a lesson that I later taught, which has to do with the negative stories we tell ourselves "under the surface," and how to address and correct them, I learned a method that has stuck with me since. The lesson was called "catch it, check it, change it," which is an easy way to remember the process. I have learned in the years since then that it goes much deeper than this, so I'll unfold it gradually here, infused with what I've learned in the meantime.
One of the main ideas of this lesson was that our brains are primarily storytelling or explanatory organs. That is, when we encounter a thing, our brain either goes "that came to be in this way," "here is what I do with this," "this is made of these parts," or some version of those. Often, we use a story of some type to explain our experiences as well. That is, our brain does it automatically. Sometimes, this results in a negative story, which can get us down on ourselves or others in unhelpful ways. The example I like to use is when I sleep in (which is a plentiful example in the story of my life). When I sleep in, my brain used to tell a story, or make a chain of connections like this:
"Oh no, I slept in! > I'm always sleeping in! > I'm so lazy! > I'm such a lazy person > I'm such a bad person!" ... and on and on. You can see how each element of my story informs the next almost reflexively, as though there is no conscious thought involved in it, aside from a kind of unpacking or extrapolation on the previous.
Somewhere along this "story" that your brain is telling, you can "catch" the train of thought. Usually this will come close to the end of the story at first, and that's absolutely fine. The idea is that you'll be able to "catch" the story earlier and earlier in its presentation. This is the "magic moment" of meditation, or of thinking in daily life. The key here is to congratulate yourself, and celebrate that you've caught the story as it's unfolding. This congratulatory attitude (I recommend even smiling a bit to reinforce it) will give a slight dopamine boost and reinforce the pathway between your conscious mind and the story as it's being told. As a conscious human being, you'll be able over time to "re-wire" the thought process, and this moment is the key to the whole thing.
When your brain is telling a story, or really doing any task at all, there's a chemical called Myelin which is released in the brain, and a very tiny coat goes around the synapses which have just fired. This will make it easier for the synapses to fire in the first place. The phrase "we get better at what we do" is universally true in this sense. Think of a time when you're first learning a skill. Any skill. It's difficult at first, similar to encountering a jungle pathway that's completely overgrown. The first time it's difficult to navigate. Maybe next time you bring a machete. After that, a lawnmower and some gravel. And so on and so on until you've created a superhighway through the brain. Think of addiction - repeated behaviors that are so ingrained with myelin that they fire almost reflexively, or automatically. And, the bad news is in this case that the body has no way to get rid of these myelin coatings. So, the good news, and the only real strategy to changing behaviors is to create a better pathway, with a better reward. That's why I suggest smiling when meditating or encountering a "magic moment" in a story. Over time, you'll build at least a bypass, or perhaps a more scenic and beautiful route to a better "destination," reinforced with dopamine, which feels good.
The next thing you'll do when encountering a negative thought process or story is to take the last thought you had (for example, "I'm so lazy!") and check it against reality. Reality is the crucial element here - rather than turning the story on its head to make it positive, examine yourself and your experiences to see whether this is true. It's usually not. So, replace the thought with what is, acknowledge the thought that was and weigh it against the truth of yourself before moving on.
Now that you've replaced that element of the story, you can look at the larger picture, and see that the story itself, somewhere along the line, became invalid. You can work, maybe with a paper and pencil even, to challenge that story overall and replace it with something more realistic, even useful.
For example: "Oh no I slept in! > I tend to sleep in when I don't set an alarm correctly, or perhaps when I drink the night before > I should limit my alcohol intake when I need to wake up at a certain time, or set a different alarm."
You can see that the nuts and bolts of this process can get complicated and even overwhelming when you think about them this way, but it always starts small. And, it's important work to do, which will reduce worry and stress on a person as they go through their day-to-day activities. The crucial thing again, whether in meditation or "waking life," is to take a positive spin on the moment which you notice the story (or whatever event happens in the rest of your day). Realize that the awareness you have of the incorrect thought is really a wonderful thing that the human mind can accomplish. That's the thing that's being worked with.
First, choose a "sacred word," (like a mantra), which you'll return to when you notice the turmoil happening in your mind, or unwanted thoughts creeping in. Centering Prayer focuses on bringing one's "whole self" into the meditation (rather than "emptying" the mind), because the work that's being done reflects back onto that self which you are during the rest of the day. The exercise is to imagine that you're in SCUBA gear at the bottom of a large body of water, looking up at the sunlight refracting through the surface of the water. Eventually you'll notice shadows (probably like ships floating overhead) against the sunlight. Each of these ships represents a thought, emotion, idea, or story that your brain wants to tell. The temptation is to swim up to the ships, climb aboard, and meet the people who are there, and explore. When you notice yourself doing this, congratulate yourself that you've noticed, and simply use the sacred word (or mantra) to recenter yourself at the bottom of the lake/ocean. Acknowledge the reality of the ship, observe, accept, and allow it to pass. Strangely, the more times you "fail" (swim up to the ships), the more practice you're getting (the more myelin you're coating the synapses with that lead from your consciousness to the story, thought, or emotion - remember "we get better at what we do"), and the more you're building that bypass or highway that is more appealing than the unwanted thoughts/behaviors.
So, maybe practice doesn't always lead to perfection, but I find this an incredibly valuable way to address and work on the difficult/unwanted parts of my own thinking, and in a sense "undo them" (though you can't really get rid of that myelin). This type of meditation is very similar to working out, or flexing a muscle, that over time will get stronger, leading to a more centered and conscious day-to-day experience. Weird to think that we're not always "conscious," and sometimes work from reflex or reaction. The goal, of course, and as always, is to become less reactive/reflexive, and more responsive/reflective.