Female fighting fish are territorial and aggressive towards other fish, including male fighting fish. If a male fighting fish is swimming away from a female, it is likely trying to avoid a fight. However, if the female is persistent and keeps attacking the male, he may eventually become exhausted and die.
To prevent this from happening, it is important to keep male and female fighting fish in separate tanks. If you do want to keep them together, you should provide the male with plenty of hiding places so that he can escape from the female if necessary.