I find that a simple way to make a health bar is to use the "slider" object, turn it sideways, and just make a method called "healthDecreaseByOne" (or "healthIncreaseByOne", if you will be adding power-ups), where it moves the knob .10 meters to the left (or right, depends on how you turn the slider). The whole slider has about 6HP with that system, with each damage being 1. If you need more health, just edit the method so that it moves to the left or right by .05 instead of .10
I try to stay away from variables when possible, so this might be a good alternative for you if you don't need a very complex health system.