I have been playing this game for a couple years now and I have been a Warrior the whole time.
I consider myself an excellent Warrior as I put time into this role everyday (with a bit of crafting & gathering on the side).
Recently I started thinking about starting a white mage class and have been thinking about it for days.
However, I just can't do it.
I go to the receptionist in Gridania and talk to the npcs and then I leave without accepting the role.
I can't play like a healer, I don't want to be level 1 again, I don't want to not tank a dungeon.
I don't want to become rusty at warrior.
I could see myself trying to tank the dungeonnas a healer cause it would feel so natural, much to the confusion of my party.
People say It will help me be an ever better warrior if I know what healers have to go through but I disagree.
As long as I do my job well it doesnt really matter what they do.
I think after many years of playing warrior only, it's too late for change.
It will take time for your mind to allow for another role to populate it(the best way I can explain that). I went through the same thing when I went WHM -> DRK, after being in the healer role across several games for close to 12 years at the time.