It just sounds right to hear "I'm thirsting in my heart" rather than "I am thirsty in my heart". The phrase is supposed to mean a person has a longing.
Maybe both are OK but using "thirsting" sounds better to me.
Maybe someone knows the correct usage?

"Thirsting in my heart" would seem more likely. Certainly "thirsting" and "longing" (and "yearning") can be synonymous in an appropriate context.


PaulM

Paul, thanks. When compared with other present participles (verbs ending in "ing") it makes sense to me that it fits.