Managing Races and Classes

[Clrobertson]

I get how almost all card management works, but I have one clarifying question about races and classes. Let's say I'm a wizard and I draw a warrior card. I want to switch to warrior, but may want to go back to wizard at another point. Am I able to put the wizard class in my "backpack," and have it for use later? Or, at the time of switching races or classes do I need to charity, trade, sell, or discard the race/class card? Thanks in advance!