Often, they end with the 'good guys' winning. For example, in 'Doctor Who', the Doctor usually manages to save the day, whether it's protecting a planet or preventing a time - altering catastrophe. His victories ensure the stability of the time - space continuum.
They often end with the restoration of the original timeline or a new, improved future. For example, in 'Back to the Future', Marty McFly manages to fix the past so that his present is as it should be. The time traveler usually learns a valuable lesson too.
Often, they end with the time traveler either returning to their original time or making peace with the new time they are in. For example, in 'Back to the Future', Marty McFly manages to return to his own time and also improves the future for his family. Sometimes, like in 'The Time Machine', the traveler continues on in the future they've reached, having learned something about humanity or themselves.
Often, they end with the restoration of the original timeline or the creation of a new, better one. For example, in 'Back to the Future', Marty manages to get his parents to fall in love as they should have, and he returns to a much - improved present. In 'The Time Machine', the protagonist has a series of adventures in the future and then returns to his own time, with a new perspective on the future of humanity.
Some end happily, with the lovers finding a way to be together across time. For example, in 'Outlander', Claire and Jamie manage to have a life together despite the challenges of different time periods. Others might end bittersweetly. In 'The Time Traveler's Wife', Henry's death is a sad but also an inevitable part of their story, yet their love remains strong. And then there are those that end with the characters making sacrifices to preserve the integrity of time, like in some more complex time travel romance stories where changing the past too much could have disastrous consequences.
They often end with Naruto having changed something significant in the past that then has a positive impact on his present. For example, if he prevented a great tragedy, his present - day Konoha might be more prosperous and his friends might be in a better situation.
Often, they end with the super villain being defeated. Maybe a hero from the future or past figures out a way to stop the villain's time - traveling madness. For example, in some novels, the hero uses the villain's own time - travel technology against him.
Many time travel science fiction novels create rules within their own universes to deal with paradoxes. In 'A Wrinkle in Time', the idea of tessering (a form of time/space travel) has its own set of rules that prevent the characters from creating major paradoxes. The characters can't just go back and change everything willy - nilly. Another approach is seen in '11/22/63' where the universe seems to have a kind of elasticity. When the main character tries to change history, the universe tries to push back and correct itself to avoid a paradox.
Some time travel stories in fiction simply ignore paradoxes. They focus more on the adventure aspect of time travel. For example, in 'Back to the Future', Marty goes back in time and there are some potential paradoxes like seeing his younger mother fall in love with him instead of his father, but the story just moves forward and finds ways to resolve the situation without getting too deep into the paradox.
They often end with a resolution of the problem that started the time - jumps in the first place. For example, in 'The Time Traveler's Wife', the story ends with a kind of acceptance of the time - jumping situation, and a bittersweet moment of goodbye.
Often, they end with a restoration of the original timeline or a new, better future being created. For example, in 'Back to the Future', Marty manages to fix the past and returns to a present that has been improved.