A white potato is extremely high GI.
The GLYCEMIC LOAD is what really matters here, and they are the same for a white and sweet potato. If anything, I feel better on white potatoes to be honest.
White rice is superior to brown rice, has a much higher GI and the same GL. If you got tired eating higher GI carbs, it's probably because you were just eating a lot more calories and it was more than your body can comfortably handle in a sitting.