Turn Parrys Into HP! (No Mods)

Life Up charm can be bought in the shop and is around 3-4 coins

The Crackshot is important to this as well

When your in combat and need health every once in a while equip these two items (They grant more health than dual hearts charm and divine relic works for this too!)
When you have a parry card shoot out a crackshot EX and wait around 3 seconds then parry it
for some reason the planets are considered to be eligible for 1 life using life up charm and now in a pinch you can follow this guide

For divine relic you already have these two enabled but a fun glitch is to do this
Parry a boss with divine relic or whetstone once its been defeated you'll notice your super meter will go up and you can shoot again so while the boss is knocked out you can beat it while it's down!