Im kind of confused about how energy shield works?

I thought aside from poison, damage was supposed to go against my mana. However, i feel like even with energy shield up, i'm being hit on my life pool (and then subsequently dying quickly)

1. energy shield transfer a fraction of the dmg to your mana. depending on the skill level of ES, this fraction can be as high as 95%, so only 5% of dmg goes to life
2. make sure you max telekinesis. this reduces the dmg to mana, so your mana pool lasts longer