Twilight Sparkle has been working herself into such a state of fatigue that Celestia has ordered her to take a five month vacation from her studies and has given Spike the assignment to ensure that Twilight relaxes. A lot can happen in five months.
"He truly loved her and knew she loved him just as much. The dragon gulped deeply as a fluttering sensation occupied his stomach. He didn't just love Twilight as a friend."