Everyone is right in a way ..
I say you should work until you have good hammer control ..and then ..while following some guidelines in books . .start making whatever you wish ...
You can screw up blades as well as nails or hooks...at first but then. . .you will be churning them out by the dozens
..
Heat treating is also important and can be practiced o stock removal blades and such . .so you don't crack a good forging.