Any major success stories here who started out VERY inflexible?

I'm talking like, super anterior pelvic tilt, can't do yoga poses like downward dog or squat/lunge with 100% perfect form... to being able to do the splits or downward dog or etc.

I'd like to pick your brain if so. I feel that the challenges of learning to be flexible, may be different for people who just have always been super inflexible compared to ... something else :P

Would very much appreciate it. I tend to be "really good" at things that I'm genuinely interested in, and I'm literally not even close to passable in terms of how limber I am, and I've been pursuing it with a daily focus for like 5 years :(