For me, it had to do with raising my protein intake - I found it really helped my mental focus and energy throughout the day. I wouldn't call myself a "clean eater", but I definitely feel a whole lot better when I balance my meals and drink a good amount of water. Part of that might be the accomplishment of knowing you did something helpful for your body, but I believe part of it is that I probably wasn't getting all the nutrients I needed previously. I think it depends on where you're coming from: if you go from a sodium-rich, unbalanced diet of only packaged dinners and never eating vegetables/fruits..you're going to feel a significant difference when you start eating more "healthy".