Healing is NOT easy!!!!

[Rein_eon_Osborne]

[...]Between dying from taking the wrong spot in fuse or foe (forgot that healers took intercards), to not healing and mitigating enough to get through fusefield cuz I tried using seraphism for an earlier mechanic, and finally dying because instead of looking at the attack name being used, I was looking at my hotbar to see what I can use to pull us through Xboom Special. Also, I didn't realize that corpses can iframe through healer LB3 when they respawn from outside the arena to the center, at which point I was flailing around desperately GCD shielding, only to wipe once more[...]

If it helps, you devise a heal plan in a rather similar fashion to devising your mitigation plan on tanks. I.e. X cooldown will always be up for Y mechanic (in its most basic sense). Failing to do that in EX or more difficult duties means you're at the mercy of whatever fight or flight response you'll likely spit out and/or your other 7 party member's competencies at covering your mistakes.

Other than that, general inexperiencedness with the role also impacts decision making i.e. panicking instead of remaining calm and collected when something goes wrong; and that's just to be expected if you don't main the role. Everybody starts somewhere.