The best advice is to create a nutrition plan and one you can stick to. I use a spreadsheet and plan the macro levels (percent of carbs, proteins & fats) then fill in the details. Right now I'm doing roughly 20%, 25% & 55%. Lots of healthy fats, no sugars except a dash of honey with yogurt and rolled oats, no refined carbs, no junk foods, no soda or juices.
Here's a great site for looking up food nutrition breakdown.
And foods for the brain.
I also pay close attention to omega-6 to 3 ratios, keeping it at 4-1 or better. A good fish oil supplement helps.