The Gemara there says, "Migmar diatikta kashu mechadita" = the learning of old studies is harder than that of the new. But I logically dont understand. If you learned something once before, it should be easier to understand than learning something new, since you did it already? I have a suggestion. Maybe it's on the decision to learn, not the learning itself and saying it's harder to go back and decide to learn something again since you did it already, rather than learning something new since everyone just wants to learn more and more with a yetzer hara to go back. Does this make sense?
Daniel Charles Fishman
There is no question that the concept you are saying is generally true. People would usually prefer learning something new than to re-learn something which they think that they have already understood. However, the Gemara's statement is "Migmar b'Atikta" which seems to deal with the actual learning, not the decision to learn. Nevertheless, you can say your explanation with a twist. Learning old material is difficult as a person does not usually have the same zest for reviewing as he does for learning something new. This makes the learning more tedious and difficult.
All the best,