I set the  forge up today and managed to get a really good heat out of it. I have however realised that my left arm is just not used to the kind of strength required to swing a heavy hammer. I can't move my left thumb any more.. :S 

Must use smaller hammer. Must ease into it  

Yes, be sure and take it easy.. You don' t want to end up with repetitive use injury this early in the game.. Take your time and move up hammer weights over a long period of time.. If the smaller hammer isn't working for you.. Move up to the larger one for a little while then move back down.. 

If you really need to move metal have a friend come over and swing sledge or keep it handy and you can use it for the bulk of forging the hardie tools.. 

Congrats on the anvil..  Double horn anvils are my favorites.. With that smaller hardie hole it will allow for so many easily forged or fabricated items for lighter work and then the larger hardie hole for more robust work..