A confusion about the fulfillment of the law

Jesus said in Mat 5:17-18 (NIV): > Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. For truly I tell you, **until heaven and earth disappear**, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until **everything is accomplished**. If we stop reading the paragraph at the first bolded sentence, we'll get the impression that the law is eternal (well... until heaven and earth disappear). But if we keep reading until reaching the second bolded text, we'll get a different understanding: somehow the law will end after "everything is accomplished" (i.e. when Christ's earthly duties are done?). So it's not eternal, after all. Isn't this a contradiction? I'm still having a hard time understanding this passage.