When looking for something to snack on during day, you want to look for foods that are high in fiber, high in protein and limited carbs.
-Almonds, Brazil nuts, Cashews and Hazelnuts are among the best health choices to keep your energy levels up.
Stay Hydrated. You need to drink plenty of water. If you need flavoring, look for flavored water, but watch out for the sugar content. Non-flavored water is the best.
If you don't say hydrated, you can feel tired or lethargic...you can get headaches and constipation as well.
Get plenty of sleep. It is shown that you need eight hours of sleep. The more you deviate from that the greater your risk of things like: depression, obesity and cardiovascular disease.
A few things to avoid are:
-sugary foods and drinks
-excess of carbs
-Caffeine
-excess of fatty foods
For some these changes are very difficult, but by taking baby steps toward a healthier lifestyle, you will start to feel better and won't miss the junk food, caffeine..etc.