Another highly simplified example of a mechanic regarded as hard to code. Quit using the Bar behavior, they work when you're new, but grow up at some point.
I present you a VERY simple and malleable healthbar example, no fuss, no muss.
Left and Right keys to deplete or increase the displayed health.
You can copy and paste the code in the Bar object straight into what you want to be your healthbar; however, you will have to take making the sprite doubled in size, then cutting that in half in an animation for its display into your own hands.
Don't bother crediting me for the code. Just take it.