backslide|backsliding

他戒酒三年后，最近又开始复饮了。

After three years of sobriety, he's started ___backsliding recently.

戒酒一个月后，他又故态复萌开始酗酒。

After a month of sobriety, he started ___backsliding into heavy drinking again.

她坚持健康饮食三个月后，最近又开始吃垃圾食品了。

After three months of healthy eating, she started ___backsliding into junk food again.