Twilight recieves a mesage from her future (mind you, not distant future, just next Tuesday morning [which by that in itself is hilarious]), and she doesn't listen to herself and keeps asking random and curious question like the bookworm she is. So Future Twilight doesn't get to finish her message making Present Twilight worried like ever. (As a side note, Future Twilight sound different, and also very, very familiar.)
Then Cerberus abandoned his role of guarding Tartarus (which by the way, nice researching, even though it is common knowledge). Fluttershy calmed him down instantly though.
Unfortunately, when Twilight came back, she accidently got a papercut, which is one thing that was on Future Twilight (which stayed on for a week, which slightly doesn't make any sense). So then she decided to do nothing to stop the future instead of doing something giving Spike the oppurtunity to eat as much ice cream as possible.
When even that didn't work, she decided to watch every single thing. And the best line in that episode went something like this: "I thought I saw something in the Crab Nebula, so I watched it for 40 hours straight, but then I realized, it was nothing!" Then Pinkie Pie made her become temporarily blind and needed to wear an eyepatch, another feature of Future Twilight.
So after "breaking in" to a powerful spell library on the night of Monday, she desperately tried to find a spell to stop time all together, but it became Tuesday morning and nothing happened. She then went back in time to warn her about not to worry about her being there, or something like that. And when she doesn't have enough time to do that, she realizes that brought that upon herself making her worry for the whole week.
So, moral of the episode: don't worry over silly things. Yeah, I'll give it 7 minutes of the next episode.