I for one found it easier to practice when the lock is mounted, at least on something...be it a door for knobs or deadbolts or a hasp for padlocks. I first practiced on rim cylinders that I mounted in my vise but that got to be too easy so I moved on to harder things.
It is true though that picking some padlocks is harder than others. I have, however, picked a few padlocks that claimed to be 'pick-proof' or contain anti pick pins of some sort. Of course most of the time a pick gun works much better with anti pick pins than a simple rake does.
Try practicing on a lock when it's 20 degrees F and sleeting with a strong North wind, that'll either make you do it quicker or give up altogether.
Good luck with practice.
{edited by Varjeal: requests for emails violates forum rules}