A little problem with variables

I’m doing a mana stuff with the variables. I used a text together with the mana variable to see if it is working. The problem is even if i use “variable is less than #” and disable the firebullet behavior,
It won’t actually disable and still able to cast spells even if mana is not enough… Resulting for the mana to go in negative numbers… Any solutions?

use your mana variable as a condition for your spells.
if mana > spellcost
action cast spell