WARNING! Spoiler alert!
So, in the season finale of The Flash, Eddie Thawne shot himself...
...in order to wipe "Wells" out of existence...
...but then, since the Reverse-Flash is from the future, and Eddie killed himself, being relative from the past, then the Reverse-Flash could not have come back because he was never born!
What that means is that, because Eobard Thawne was never born, he could not go to the past and switch places with Harrison Wells, which means the particle accelerator would not fail, which means no lightning storm...and no Flash.
So, shouldn't the Flash have been erased from existence as well? Or even the whole time line? That technically should have reset because the Reverse-Flash could not kill Barry's mom, so Barry never would have moved in with Joe and Iriss. Everything should have been different!
To "better" explain (still confusing as hell and hard to explain), here is a video: