I think that, if religion is going to play an important role in your relationship, it's doomed from the start. Even if you both profess the same religion, chances are pretty good that your actual beliefs will differ in some ways, if not in most ways. If either one of you is going to insist on your partner believing the same thing then I doubt any relationship can be stable.

However, it is possible to keep religion out of the relationship, except as a side issue. If your partner wants to attend services, let him/her. If you want to attend different services, why not? Or, as in my case, not attend at all.

My wife and I were both non-practicing Roman Catholics, and we have not attended a Mass together since we were married. She occasionally goes, but not very often. I have become an atheist. Yet we stay together, in love, because the other person's religion doesn't mean a damned thing to either of us. She doesn't ask me to go to church, and I don't ask her to give it up. She wants to decorate the house for Xmas, so I let her. I don't help, except to bring things in from the garage. And take them back when she's done. Religion has no meaningful place in our house.

I think a mixed marriage can work, as long as neither person is placing their religion above everything else.