It's all about the problem. What "problem" did the first Twilight have?
Unfortunately, the next Twilight thought it was a disaster. She overreacted, and came to the conclusion that Future Twilight was trying to warn her about not worrying.
This could be true. The first Twilight might have had a story similar, an overreaction that taught her not to worry about the future, so she told her past self so she didn't have to go through the same stuff. On the otherhand, something terrible could have actually happened. Perhaps Past Twilight did something she didn't pay attention to that prevented the disaster?
We'll never know. :c