Balancing nutritional values

If this topic has been raised and the thread is buried somewhere, please do bump, but in the meantime...

My question to you all is how do you get the right nutritional intake? For instance - our fats are carbs are typically quite low but the calorie intake is so high that I personally don't know what I should be eating to meet the calorie intake without going crazy on the carbs and fats. There are days when I feel like I've eaten heaps, I'm under the goals or just meet them and I'm still not at the calorie target. Then, on other days, it's like I haven't eaten anything and my calories are dangerously low but I've eaten something high in fat or sugars (I've been eating a lot of fruit and nuts lately - who'd have thought that'd be a bad thing?!) Am I making sense? Should I be eating more protein, maybe? Help. :(