Personally no. I normally do my "meditation" at the start of yoga practice and count breaths, so I'm not very helpful on that front unfortunately. I've had people suggest Smiling Mind. Haven't really used it though, so can't vouch for it. For just taking moments out of my day to breathe properly though, I like to use Nathan W. Pyle's animations on Twitter - I find 'em really soothing.
EDIT: I was dissociating really hard at the start of Stage 4 and definitely as a self-defense mechanism. Wish I had some pro strats to give you about grounding yourself but one of the weird things that helped me was getting one of those meal boxes (like HelloFresh?) and just working through the pre-prepared recipe. I normally like cooking though, so I wonder if it helped because it put me in a situation that was very "me" but at a relatively low mental load (plus a tasty relatively healthy meal at the end). YMMV.
A well rounded view of life, and understanding how to look at adversity and how to survive (and even thrive) through it.
I was in a funny head space a few years ago and this book helped me a lot. More Than Happiness: Buddhist and Stoic Wisdom for a Sceptical Age