I've been doing it off and on to varying degrees for over 10 years, more intensely lately as part of mindfulness based cognitive therapy. I'll throw in some anecdotal stories:
- Feeling anxious, stressed, or grumpy, realizing it, taking a moment to take a breath, let my shoulders relax, and trigger myself to become calmer and more collected. Two years ago I experienced a life-altering situation involving a medical situation with a family member that involved basically non-stop stress for a full week. Every single day when I got in my car to go home I just broke down crying in a way I've never done in my entire life until then, and then every morning it felt like I had to reassemble my component parts to become a functional human again and do what needed to be done. Being able to center myself and keep my anxiety and stress in check when it was at risk of running away was hugely important not only to getting through that experience and having it strengthen me rather than destroying me but also to getting the things done that needed doing (which had a positive life-altering impact on my family member as well).
- Something as small as coming out of a grocery store and being disappointed by the rain then taking a moment to breathe and relax then walking through the rain and just accepting it without feeling annoyed or inconvenienced by it.
- Something as big as feeling a big self-critical thought bubble up in my brain, the sort of thing that could easily cause a plunge into a depressive mood for a while, acknowledging that it's just a thought and that it is neither intrinsically true nor intrinsically something I have to get caught up in, then feeling it dissipate and go away, powerless.
- Being able to recognize when I'm living life too much on autopilot then having the ability to basically reach out and turn up the volume dial on experiencing the world.
If you work on it enough you get to a state where you can reach into your toolkit and pull out various tools to deal with different experiences and situations. Being able to recognize those situations as amenable to tool use and being able to actually use those tools and watch them work can be enormously empowering and satisfying.