A big trap new tanks make is using cooldowns reactively instead of proactively. Most tank classes have an ability that reduces damage by 50%. New tanks consider cooldowns as “oh XXXX” buttons. Don’t fall for this trap.
Let’s do some napkin math.
You’re at 100% health. You take a big hit and now are at 20% health so you press your big cooldown and effectively have 40% health before you die. 50% damage reduction and only 20% health so it takes damage equal to 40% of your health before you die. You used it reactively.
Now let’s look at it proactively. You’re at 100% health and use the cooldown. You take the big hit but at 50% damage reduction you’re still at 60% health and you require 120% of your health to die while the cooldown is still up.
Use cooldowns proactively so you can survive. Your healers’ mana will last longer and they won’t have to cover for you.