The first verb in a sentence establishes the tense of any verb that comes later. If you begin writing in the past, don’t change to the present. Similarly, if you begin writing in the present, don’t change to the past.
Incorrect: In the story, the king loses his kingdom, but he regained everything in the end.
Correct: In the story, the king loses his kingdom, but he regains everything in the end.
Incorrect: The team won yesterday, but goes and loses this afternoon.
Correct: The team won yesterday, but went and lost this afternoon.