The anchor text
Read what it actually says. For everything there is a zeal, and for every zeal there is a slackening. The report does not ask whether the slackening happens. It takes that as given, and asks a different question entirely.
Qur’an and Sunnah
Abu Hurairah narrated that the Prophet (s.a.w) said:"Indeed for everything there is a zeal, and for every zeal there is a slackening. So if its practitioner behaves properly,and is moderate, then hope for him (for his success). But if the fingers are pointed to him, then do not count him (among the worthy)." It has been related from Anas bin Malik that the Prophet SAW said: "It is sufficient evil for a man that fingers be raised against him, regarding religion or worldly matters, except for one whom Allah has protected
Jami' at-Tirmidhi 2453graded sound, albanifull report