My partner and I have totally different money habits. Marriage soon.

Married 6 years, my husband was the spender. What saved us was the "three pots" system. Joint account for shared stuff (rent, utilities, groceries, insurance) that both top up proportionally to income. Then each person keeps their own personal account for guilt-free spending, no questions asked. Third is joint savings for goals like the flat and holidays with an agreed monthly amount. The key was agreeing on the shared and savings numbers first, then whatever's left in his personal pot he can blow on gadgets and I won't nag. It removed 90% of our fights because we stopped policing each other. Have this conversation before the wedding, not after. Money differences don't kill marriages, but hidden spending and resentment do.