Blessing of Fortitude

From within the caster's body light swells throughout blessing them with newfound fortitude. The caster gains 3 ability score to their Constitution. Any remaining bonus health after receiving damage is lost after the duration. This cantrip may only be used once per long rest. 

Cantrip Upgrade. The spell may be cast an additional time when you reach levels 5 (2), 11 (3), 17 (4).