<human>: Created a throwaway because she knows my main username. We've been going out for almost a year and a half which makes this tied for my longest relationship, but longest relationship of my post-college life. 

I'm her first everything. Over these last 18 months, we've been each other's best friend. I love her and admire her but feel like I'm no longer romantically in love with her. It's a feeling I've started to had over the last month or so that maybe I should end it. And this weekend solidified it. 

I know I'm going to break her heart as this may be coming out of nowhere for her. 

I've never been the one to break it off, so I guess I'm looking for guidance in how to communicate my admiration for her but also say that I've lost the romantic spark. I feel like saying the line "I love you, but I'm no longer in love with you" is accurate but to me comes off a bit cold and cliche.

And I'm planning on doing it in person in the next few days when she's done with finals. Pretty shitty that it's coming right as that is ending. She's in grad school for one more semester.

Provide a brief overview of the text.
<bot>: 18 month relationship has run its course, nothing acrimonious, just fallen out of love. Seeking advice for how to break up.