I too felt this a lot before and one thing that has tremendously helped me is not eating lunch in the afternoon. I only eat when I'm extremely hungry during th

I too felt this a lot before and one thing that has tremendously helped me is not eating lunch in the afternoon. I only eat when I'm extremely hungry during the day time and that too just enough (like 1/3 full). I dunno but this keeps me super energetic and happy during the day.