Health & Energy

Health and Energy are a hero's most crucial resources, and you must monitor their levels constantly. Health keeps you alive, and Energy allows you to harness skills that increase your offensive and defensive capabilities in battle.

Both Health and Energy regenerate over time (though Health only regenerates when you're not taking damage). While some skills can assist regeneration, others can cause Health or Energy levels to degenerate. Hover the mouse pointer over a skill's description to find out its Energy cost. http://www.guildwars.com/gameplay/combat/stayingalive/