Mood swings

Healthy relationships need effort in the sense that you want to prioritize spending some time together and connecting in the midst of life’s other obligations, demands, and stressors. It’s not that the dynamic of the relationship itself should constantly need work like this just to function without being unhappy.

Your problems here are legitimate and not small because it’s a long-standing pattern that both upsets you and brings up your own baggage that probably hasn’t been been fully dealt with (it’s likely not a coincidence that you grew up dealing with your mom’s unpredictability and then found a partner who is the same way… it both makes you unhappy and uncomfortable but is also totally familiar to you). You shouldn’t have to deal with this if it never changes, because that won’t be a happy life. It will damage your trust every time it happens until there’s none left, especially since you’re right: he’s a 30 year old adult and should be taking responsibility for his own issues!

The only way this changes is if he wants to change, and you’re both equally committed and individually motivated to deal with each of your baggage from before the relationship that’s causing this. What did he go through growing up that causes him to have uncontrolled mood swings? If he has mental health issues then it is what it is, but is he managing them properly (from your description, it sounds like no)? You don’t need to enable or mother someone or be a punching bag for someone who is actively not trying to get help to manage their own stuff. And on your side, you accept the merry-go-round even to your own detriment because you were conditioned to do so when you were younger.

Are you in a country that has couples and individual therapy available? If not, maybe there are remote options online? Is he willing to take a hard look at himself and make some changes, including trying couples therapy with you, if you tell him you’re unhappy with the way things have evolved between you? (This is different than saying you don’t like him, it’s telling him you don’t like his behavior or how you feel after it happens.) Are you willing to speak to someone on your own about resolving leftover challenges from your mother and learning to trust yourself enough to depersonalize and have good boundaries when someone else is taking their issues out on you?

If you’re both not willing to do the work on yourselves, the relationship isn’t going to get better, and you should start building a support network and life for yourself outside the relationship to eventually leave. Staying because it gives you some stability that you’re scared to create on your own isn’t a good reason to stay and be miserable. However, if you prioritize that stability and do stay for that reason, then you need to take responsibility for that decision because you are choosing it. At that point, it’s not just him doing something to you or thinking about the relationship as needing work, it’s you knowing exactly what you’re signing up for and deciding it’s worth it even if it never changes and gets even more like it currently is over time.