Admittedly, I've now watched this twice this week already.
When I first really started getting into anime in 2008, the first Rebuild film had come out not too long before and I dove into it. I loved every second of it. I picked up the series and watched it countless times (partially because I had a small download limit at the time, per month). It fascinated me. The world was something special.
To finally finish the series after 13 years feels like a chapter of my life just closed. Despite all the things the third film felt like a flop on, Thrice Upon a Time redeemed every bit of it. It felt like a send off for the characters, for the fans, and a real closure to the series. I'm still struck by how hard it hit me to watch the credits roll and think of the impact it had on me, and for it to now end. It feels like a real hole in my heart now.
It could still take a bit for me to get over this - but I know it's something I'll rewatch just as many times as I did the series.