Understanding conditions (Disease, weakness, posion, bleed)

I am trying to better understand conditions. Like for instance, under disease, it says lose 4 arrows of health...what is up with the arrows? I see them on my bar but I dont understand how good the dmg really is for one of these conditions, what exactly is 4 arrows to a person with 500hp. The same for weakness or posion. Can anybody who really understands the conditions, their benefit and dmg, please help me out here?

Each arrow of HP is 2hp per second. Each arrow of energy is 1/3 energy per second.

There are arrows that can appear on your HP and energy bars. arrows going to the right (>>>>) mean that your gaining more energy or HP and left (<<<<) means your degenerating energy or HP. The more arrows the faster the degeneration/regeneration. THink of it as this:Arrows going right means GOOD. Arrows going left means BAD.

Regen/Degen seem to be very powerful in the early stages of the game, and get less and less so as time goes on. Because low-level characters and monsters have low HP, conditions that cause degen will remove a significant chunk. The Mesmer hex "Conjure Phantasm" is a good example of this; in Pre-Searing Ascalon it is trivial to kill enemies using just this spell. Past about level 8 or so, it becomes vastly less powerful.

As someone mentioned before, regen/degen is 2 HP per second or 1 energy every 3 seconds, per arrow. It's capped at ten arrows, I believe, so you can't lose or gain more than 20 HP/second due to conditions and hexes.