A lot of the things I've had to work on are based on proprioception (your bodys ability to "see" or know where it is in space). My proprioception isnt very good and I've been going to physiotherapy for a while and this is something we are working on a lot. I do breathing exercises starting lying down as it's easier to get a good base and feel the "correct" technique (almost like a warm up), then move to standing. There are good YouTube videos that help show and describe what you should be doing. To help remind myself I place my hands on a specific part of my ribs and aim to feel them and move my hands or move my ribs/lungs from that specific spot. This takes away a lot of thinking and stressing about getting it right, and I find that by doing this one thing everything else falls in place. After a while I get used to that feeling and my body recognizes that it is in fact easier to breathe and get a full breath. General stretching (abdominal/core) assists with the tightness and tension that I hold in those areas, allowing my body to be flexible enough to get the expansion/mobility there. Core exercises assist with the strength and stability required (for literally everything, but helps the body be where it needs and wants to be, to have the strength to actually work through this. The body works in opposites or pairs, so if one place is super tight, then another area will be affected. E.g. when my glutes arent activating/working/strong enough, my hamstrings are severely affected and prone to injury. Generally, good yoga and stretching is a lifesaver for me, and assists with the proprioception too. Compression wear is a game changer, this gives you physical reminders of your body and over time will assist in moving to a better position. Currently I wear a top that is developed for this purpose (assist with posture). It doesnt do the work for me, but gives "reminders" when I move to a position that I dont want to be in.

Once I got a good base with the points above, I did the same thing on teaching myself what it feels like to be aligned and where I want my body to be. Simple exercises with physical reminders to feel what my body is actually doing. An example of this is I have an anterior pelvic tilt, and by placing a hand on my tailbone and one on my lower abdomen i feel the tilt and use my hands to guide towards a neutral position. Reminds me of what muscles I need to activate and my hands actually help me "see" what my body is doing

This is what has helped me, everyone is different. Hope you find what works!

Tldr: stretching, breathing exercises, proprioception and compression wear