A month-long conversation followed by rejection

At a friend's suggestion, I created my Hinge account back in November. He and his girlfriend had met each other through the app. I'm incredibly picky when it comes to dating. Thus far, on 99% of profiles I've clicked the 'X' button; and that's after the app's shortlisting to meet my stringently defined dating preferences.

Back in December I (40M) matched with someone (35F). We have very similar backgrounds (i.e. social class, level of education etc) and interests. Our conversation started off with a discussion around books on our reading lists. I won't say it was a deep conversation, and yet it was far from superficial, which I found refreshing. When I really click with someone, my brain starts telling me I must to do everything to win them over. We exchanged messages for well over 4 weeks. I work in a rewarding FinTech sector job in London, have an incredibly busy daily schedule and precious little time for myself. And yet I always did my best to get back to her as soon as I could. I was genuinely looking forward to meeting her in person. Finally when I did ask her out she dropped the bombshell and told me she only wants to remain friends. Her message flashed up on my screen just past midnight last Saturday. I couldn't sleep that night, left home early and spent all Saturday in the city just to keep myself busy. Around midday, I finally decided that this couldn't go on any further. I texted back and told her I wished her all the best in her search and that should our paths ever cross in real life, I'd be happy to say hello.I could only ever think of a romantic relationship with this woman and therefore settling for mere friendship was simply of question. And it's not her fault either.

It's been the most difficult weekend for me. I met a friend over lunch, spent the afternoon at an art exhibition, and the entire evening browsing through books at a bookstore until their closing time (2100 HRS). Then I went for a very long, contemplative walk along the river and only returned home around midnight. It's taken me 2 days to get over the initial shock. How could something with such a serendipitous beginning, end like this?