The expulsive power of a new affection

I'm writing this up while watching an episode of Breaking Bad, so this might be a little distracted.

Last semester, one of my professors recommend we read a sermon/article by Thomas Chalmers called The Expulsive Power of a New Affection. I noted it in my phone and a few months later, about a month ago, I found a pdf online and downloaded it. I read a couple of the pages and basically the guy talked about how you can't just stop caring about something, there has to be something you care about more that will replace it. In the sermon, he talks about Christ being the greatest affection to cast out all others. On top of that, however, it got me thinking about how it's been like that will all the girls I've liked. T went to M went to K went to R went to A went to C. Now, it wasn't always solely a new affection that helped me move on from someone. Sometimes I focused on the negative things or the differences, other times I just focused on something until the she of the time was out of sight and out of mind.
Now, I'm writing this post not because I've moved on from C (I still care about her a lot) but because even though I feel like I'm in a hopeless stand still with her, there's still life in my heart. Yesterday and today I went to the park to read some of the Iliad for my class and both times I saw and subsequently greeted a pretty teenage girl who was at the park with a mentally challenged guy who I assume is her brother. Now, she's probably just a high schooler and when I go back tomorrow to enjoy the weather and do more reading she probably won't be there, but my point remains. When I was walking back to my car and saw her and she saw me and she said "Hello again" and smiled, I felt light-hearted and hopeful for the first time in a while. The situation with Girl C has been pretty stagnant lately and we hardly talk, so I've felt kinda somber over all of it, so feeling what I felt by just exchanging hi's with a pretty girl at the park really made me feel like even though the short-sighted view I have feels like I'll never move on from this girl who doesn't feel anything for me back, there's still hope in the future, even if I don't see it or it's a ways off.