Too much Caffeine makes me feel very "unsettled" - which is the only way I know to describe it. I limit myself to 2 cups of coffee a day and none after 9 AM. I've found even if I have only 2 cups but still drink it after around 9 AM I still feel unsettled. Don't know why. After that its water or decafe herbal teat the rest of the day.
Sugar - man, don't get me started on sugar - lol. Even a little makes me feel like my heart is going to jump out of my chest. It really sets me off. I do my best to avoid it completely. The sugars I get occur naturally in fresh fruit. Took me a LONG time - and a lot of panic attacks, and heart attack fears to figure this one out but now that I have I feel 10000% better for it. Remember, sugar hides in places you don't think - pizza, breads, pasta, etc., pretty much all get treated like sugar once you eat them.
For carbohydrates "low and slow is the way to go"