Get in the habit of checking the energy content of the products you eat - per portion information may be more useful that per 100g, but do check how the manufacturer’s portion compares with the amount you actually eat.
Constant calorie counting isn’t necessary, but it’s good to be aware which foods are high-calorie, and that this can vary between the same type of products. Get in the habit of checking the energy content of the products you eat - per portion information may be more useful that per 100g, but do check how the manufacturer’s portion compares with the amount you actually eat.