Can't say I ever had an effect relating to chocolate. While I have nights where I toss and turn because I imbibed too much caffeine too late in the day, I can't trace any of that to consuming too much chocolate. Unless you prefer really dark chocolate with high cocoa content, the caffeine isn't that much either. Wikipedia says a regular bar (100g) contains about a third up to sixth of a cup of coffee or third of an espresso shot.