Its effects vary. My programming productivity drops when I'm on caffeine because I get anxious. It makes me procrastinate a lot more because I get intimidated by the work I need to do.
I find that green tea is often more useful than coffee if you just want a mild push, since it’s basically low dose caffeine. It also has L-theanine which is a mild anxiolitic and can counter caffeine’s anxiogenic effect. Some also find that taking an L-theanine supplement (OTC) along with coffee can also counter most of caffeine’s anxiogenic effect while keeping the wakefulness and focus.
