Board Thread:Theories and Speculation/@comment-31099706-20170327120301/@comment-734582-20170520084623

Ahem.

Naruto chapter 142, page 15.

Itachi: "Only another sharingan user could fight me. [..] however this sharingan has a special eye jutsu. My illusion Tsukuyomi cannot be beaten, only a sharingan user with the same blood as me can defeat me". There, you have it. Sasuke broke through it naturally. Given that he met itachi's specified conditions and also was subjected to it a large number of times, it would be crazy if he was still vulnerable. We've seen people adapt to ninjutsu after seeing techniques only a few times.

You can interpret Itachi's reaction however you like. Possibly he subjected Sasuke to it in order to train him to overcome this ninjutsu. But Sasuke's been in Tsukuyome before, Itachi wouldn't be able to deceive him with a less than full strength one.