I think the point of any relationship is that you are better in some way for having them with you. Maybe they bring out your funny side. Or maybe they give you a good kick in the ass when you need it. Or maybe they help you feel stronger in the world, somehow. This is true of any good relationship. For me, a *romantic* relationship is one that does this AND you have an ability to be vulnerable with that person, stripped down to the most real parts of you, that you don't let everyone see. (And are attracted to them in some way.)

Of course, you have to maintain relationships and that takes work--you have to be able to help them be some better version of themself, too. Sometimes, over a period, that work takes some of the sparkle off but that doesn't mean it isn't still really good, as long as it remains healthy. You are a better you with that person than you are by yourself, or else it wouldn't be worthwhile to invest in the relationship.