There is two types of theories about the future.
Predestination states that the future is set in stone. Everything that is done to reverse the course of future events only seeks to ensure it's continuation. Keep in mind that future events in our view is looked upon as past events for others.
Another theory states that the future is a blank page which has yet to be written. Efforts to reverse the course of future events erases the old timeline and creates a new timeline. One wrong move done the wrong way and a beloved timeline which has captured the imagination of the general public is gone. One wrong move done the wrong way and a beloved timeline which was the focus of films, television show episodes and songs is gone forever. And the new timeline also might capture the imagination of the general public. And the new timeline could also become to focus of films, television show episodes and songs too. But the way the new timeline is worshiped and revered won't be the same.
The trickiest part of time travel is making sure that you don't accidently erase the timeline that you came from. Saying and doing anything that isn't part of that timeline regardless of your feelings on the matter could have horrible consequences. It's tough to travel backwards in time and tell somebody from the past that they will need to figure it all out on their own without your help. The hard part is realizing that it's better that way to ensure the survival of the time and space continuum. That's why the number of time travelers currently operating has always been few.
And as I'm lost in thought about the past, the future and everything else in between, here are some photos of Rachel Nichols.