At the end of season 1, The urge to defeat the "reverse zoom", and events where he found out the day his mother was killed, among 2 speedsters, he was there from future, it made him break the time barrier.
Later he comes to know, Barry didn't go to past to save her mother rather went to kill her. His mother being murdered was the reason that lead him to become "The Impossible". Dr. Harrison a.k.a Reverse Zoom wanted to remove the existence of Flash by saving her mother. Changing the timeline entirely.
In season 2, after finding that, Barry(Flash) gave up and returned to his normal life considering he was destined to be a bad person. But later as season proceeds, he finds that, city needs him, city needs the flash. The same flash who always come to rescue and protect from evil. He realizes, future cannot be predicted what he will become but his action towards fight for justice and against evil in present will decide what he can be.