Sophie Gastman tries to balance protein, fiber, carbs, and healthy fats in every meal, and she’s not scared to use convenience foods and store-cupboard staples when she’s low on energy or time.”There’s a lot of guilt that comes with buying certain ingredients,” Gastman, a nutritionist who fights misinformation and the author of “Find Your Healthy,” told Business Insider.Leaning on store-bought foods like fish sticks might be the difference between you making a homemade meal and…