Season two of DC's Legends of Tomorrow was a learning curve for Sara Lance (Caity Lotz). She went from being the assassin/monster to being the captain of the ship and in charge of a group of less-than-efficient heroes who tend to mess things up more often than help. It was quite the learning curve, but by the end of the season she'd gotten pretty good at it — enough so that Rip Hunter (Arthur Darvill) no longer felt he had a place on his own ship and left.
As we move into the third season of the series, Sara will be much more comfortable being in charge of the Legends, but she is also dealing with guilt over just how screwed up the world had become and how she sees it as her fault…how her actions led to where they were. Executive producer Marc Guggenheim told EW.com about Sara's motivations for season three:
"She's found her place as the captain of the Waverider, so unlike last season where it was a little bit of a learning curve, she's happy to be the captain. One of the things that hang over the whole year is the fact that she has some measure of responsibility for all the anachronisms that they are dealing with."
I'm guessing that this isn't a matter of them fixing one thing and it dominoing through the timeline, but rather a series of breaks in time. At least that would make more sense.
DC's Legends of Tomorrow Season 3 premieres October 10th on the CW.