The joy comes if I had trouble making the ship happen. In many of my shorter works, it falls into place naturally, where the events make sense of the chemistry between two characters. In my Passion Project, it was like this before I made a huuuuuuge change that meant rewriting book 1. Now, all of the scenes that would make sense of a romantic relationship between the lead and her co-lead are not there, and it turns out there's a stronger on-paper relationship with someone else in book 2. Then, because of the events in book 2 that take her out in book 3, there's no time for building more between her and the co-lead.
They don't even have the opportunity for romance to happen between them anymore, but they have so much chemistry that I refuse to let it go to waste. I've been tearing my hair out trying to figure out how to let it happen in the series, without it happening so late in the series that I'm dissatisfied. I know that when I figure it out, I will be beyond rejoiced, and I will definitely feel like a matchmaker who just found a way to let two lovebirds be together .
I tend to get the most joy out of seeing other creator's ships happen (if, of course, they're the ship I was rooting for xD) as opposed to my own. But gosh do I look forward to the day my project falls into place...