Calling an attack function.

This is killing me.

In my update section I have various functions. The the player is in the vicinity, move towards him. When close enough, attack him.

When the attack happens I want a registered hit of health from the player. So if the player has 20 power, it gets -5.

Then the key is I want to wait 3-4 seconds and take another 5 health away.

I'm using javascript and I've been exploring coroutines using the yield statement. But it isn't working as I want.

Right when the enemy attacks all my power drops and I die. I know this is because the update is called every frame, so it's an instant decrease of 5 health over and over.

How can I fix this?

There is something I'm not getting. I understand why it's happening but am having trouble fixing this.

Please walk me through any ideas with hand holding. I'm a noob.