I waited to the last minute to print many of these for Valentine's Day favors…well despite seeing the gaps between the pieces as they were printing, they fused too tightly for some normal prying.
Use the jig with a ramrod-type object like the metal or wooden handle of a kitchen utensil and apply pressure on the outside curve to pop them free. Concentrate force on the inner heart on the left side, and for the middle heart use the right side (see cover photo).
It's probably not necessary to force pointy objects between them, as my wife did (reason why the cover image print looks chewed up). If you're still getting lots of resistance, let the hearts sit in some near-boiling water a few minutes and pull them out to cool and try again. Slight shrinking in the XY might get you enough wiggle room to begin.
The author remixed this model.