Like trab said, you should feel pretty good while on a run of test. And like ST mentioned, diet can effect this greatly...blood sugar crashes are largely responsible for a lethargic feeling...and this can occur on a bulking diet as well as a cutting diet.
The only AAS that has ever made me feel lethargic is Dbol, that's why I don't use it any more. But I'm in the minority when it comes to this side effect from Dbol.