So time travelers will find themselves "haunted" by "forces' that keep them from performing certain acts and going certain places.saying certain things Because if they did, it would make a loop that made them":not be there" by virtue of being dead, non existent or affected the time of the time trip---Now since such a loop will NOT play itself out, in real life, they are simply stopped in their tracks when they try to do something that could loop on them. ----No magic here , but simple cause and effect, if you think about it..
The farther back in time they go, the stronger and more frequent this restricting "Time force" will be. Whole countries may be off limits at a certain time distance, and one might have to go to places like the Globi Desert or someplace, to be able to go back in time and not affect their future.
The Grandfather Paradox is a logic error---asking what would happen if you did something you wouldn't be there to do. It is taken one step too far---Even Einstein missed this one, You could no more pull the trigger on a gun pointed at your Grandfather, than the wired relay switch could turn itself off.
Indeed this effect might be so "tight" as to be what keeps us moving one way into the future to begin with---Past travel might not be possible at all in most locations