I wouldn’t say it’s similar to your experience since the dude you tried to help never put any effort to change. ML in this story did, with the support of the MC he realized that there was more to life than that egotistical priestess. You leaving that dude was perfectly fine, he wasn’t putting in any effort to change and people should never stay in a relationship that is making them miserable. In real life, both parties have to be mentally well/mature to be in a relationship and it end well.
Emotionally unstable people need to work on themselves before seeking a partner.
But that doesn’t mean you yourself should enter a relationship with someone on the stance of wanting to help or fix them. The chances of that ever working is very slim which is why it leads to way more problems than solutions.
After coming back re-reading this after a year, I noticed this is similar to what has happened to me. Getting close to a guy who's heartbroken, depressed, and have a suicidal thoughts. Find myself in a situation that i feel like i need to give him the support that i can give to cheer him up. Accompanying him to recover bit by bit. But i ended things with him because unlike kael he doesnt put that much effort to change and recover despite all the supports he received from people around him. Call me cruel for leaving him, but in the end I'm not Hestia that has kael as her own world, there are many things in life that i need to prioritize than a guy who doesnt have an effort to recover.
On that note... after so long re-reading this I didnt noticed that they have 3 grown ass kids now and super adorable toooooo(´艸｀)