This charm is quite potent, despite the fact that it breaks upon death. One way to make use of the charm is to only use it in situations where dying is unlikely, such as exploration, in tandem with survivability-increasing charms, while avoiding its use in boss battles, except for Dream Boss battles (as the charm will NOT break when dying to these bosses).
The obvious downside is that once broken, Leg Eater will only repair it for a price. Late-game, the Geo may not be much of an issue, but the trip will be.
Lastly, it should be noted that its drawback is completely negated in Steel Soul runs since the run is over upon death anyway, making Fragile Heart a much more useful charm on a Steel Soul run.
How to Acquire
When broken, Leg Eater can repair it for 200, or for 160 while wearing the Defender's Crest.
Once the Knight has summoned the Grimm Troupe, Divine becomes accessible in Dirtmouth. To get the unbreakable version of Fragile Heart, the player must equip it then when speaking to her, give it to her when prompted. She will eat the charm, then ask for 12000. Once the Geo is paid, she gives the player the unbreakable version of the Fragile Heart charm.
Useful to combine with Hiveblood during exploration and backtracking as it will slowly regenerate health, however it should be noted that it will only regen the last health point lost.
Joni's Blessing will include the Masks given by Fragile/Unbreakable Heart when calculating its hp bonus.