Concentration in Zikr

Hazrat Mufti Ebrahim Salejee (Daamat Barakaatuhu) mentioned:

A person making zikr does not always gain the concentration and presence of mind that he desires. Hence he thinks: “What is the benefit of such zikr?” and contemplates on abandoning it. This is purely a whisper from Shaytaan and one should not pay any attention to it. Rather, he should continue making his zikr.