Paradoxical Loops
Warning: Time travelers, beware! Entering a paradoxical loop can have unintended consequences.
You may find yourself stuck in an infinite cycle of reliving the same moment, with each iteration slightly different.
Example:
A man travels back in time to 1955 to prevent a disaster, but every time he tries to prevent it, he creates a new reality where the disaster occurs in a slightly different way, causing him to travel back in time again, ad infinitum.
This can be very frustrating and tiring.
So, be careful when dealing with paradoxical loops. You may want to stick to linear time travel.
Sub-loops for more information.