The reason why Wang Datou is afraid of Sasha's loss

Because Wang Datou likes Sasha very much and doesn't want to lose Sasha.

The reason why Wang Datou is afraid of losing Sasha is because Wang Datou likes Sasha very much and doesn't want to lose Sasha. Sasha is a very lovely girl. When Wang Datou and Sasha are together, they feel very happy. Therefore, Wang Datou doesn't want Sasha to leave himself or lose Sasha.