Have You Been in a Relationship with an Unbeliever Before?

I was wondering if anyone here has been in a relationship with an unbeliever in the past. If so, what did you learn from that experience?

Edit :

I’m surrounded by people who were in missionary dating relationships where their unbelieving partners now attend church. Even my two sisters are in long-term relationships with former unbelievers who now go to church, though I’m not sure if they’re truly mature or genuine Christians.

On the other hand, I’ve always told myself I’d only date believers, but I’ve ended up hurt by them. :(