Question for fisters

So finally, in the last couple of months I've successfully taken a whole hand in my arse. With one lady it turned out to be quite easy as she had very small hands. With a couple of others it was hard work and in both cases it seems to cause quite a bit of pain to the hand; more than it was hurting my arse (not much at all and worth it)

It hadn't occurred to me that fisting could be painful for the fister - I've never done it. Anyone else experience this? Are there ways of going about it that are less uncomfortable?