Fascinating.
Logic dictates that, whatever the caffeine level may be, coffee is a superior beverage that is 'far' from reproach and conclusively incapable of causing error.
My suggestion would be to look elsewhere for the causal effect.
How can anyone, in reasonable command of their faculties, even consider questioning the involvement of coffee in regards to being 'unsuccessful'. Highly illogical.
Side note: (factoid)
May I also suggest that, one switches to tea, as it contains only 11mg of caffeine per 100gms of tea.
Both the U.S Department of Agriculture and the European Food Safety Authority define 'a safe caffeine intake' as up to 400 mgs per day, 200 mgs per single dose, or 3mgs per kilo of body weight. One cup of coffee can contain 47mg of caffeine but can contain as much as 90mg. Whereas tea contains 20-45gms per cup.