hi ;-) a few things i would recommend, decent leather, if you havent tried them,try theidentitystore.com i never have any trouble carving on their leather, i always had trouble with the standard swivel knife blade so i tried one of the angled ones which made a huge difference to my control of the blade,especially with tight bends and curves etc. and dont try anything too complex to start, keep them simple, this was the first carve i did that i new i had the hang of it
and this is what i juat finished this evening
and lastly yes.it is all to do with practice,one other thing, try using a pen instead of a stylus, you can see where your tracing amd what you might have missed before you remove the paper to look, most of all keep at it,you couldnt find a better way to waste time lolol ;-) good luck