Leave room in the budget for pleasures neither partner has to defend as useful.

Money conversations tend to be won by whoever can argue usefulness. Practical items are easy to justify and pleasure is not, so the things that make a life feel like a life get debated and quietly dropped. Over time a household becomes efficient and joyless without anybody choosing that. Some spending should not require a case to be made for it.

Agree an amount each of you can spend without explaining it, however small. Then let the other person’s choices go unquestioned, especially the ones that look pointless to you.