What does "Oblivisci tempta quod didicisti" mean?

It's a Latin quote from an Epica song. I know enough Latin to make out that "oblivisci" is the infinitive ob "obliviscor" (I forget), and I know what "quod" means, too, but my dictionary holds no words which could be conjugated or declensed to become "tempta", and as for "didicisti", it seems to be a form of "dido" (I spread), but I don't know which form... So, what does it mean?