Why is it so hard to lose weight

I have been eating so much lately and not disciplined at all in keeping to my calorie counting diary, which surprised me when I weighed myself this morning and found that my weight dropped though it is still hovering a little above my goal. 

With that I shall adjust my goal to a new one, -3 kilograms on top of my current goal and get back to logging in all my food intake on a daily basis. 

I use the MyFitnessPal app which is very versatile. It provides a wide array of food with its nutritional values that you can search and add into your daily calorie intake. You can also add your own foods.

I started doing this September last year and I lost 10 kg in 12 months. But my colleague started on a fruit juice diet and he lost 6 kilograms in just 2 months. I really don't know how they do it. 

Whatever it is, I need to get back to my daily discipline of limiting my daily calorie intake and stick to it to lose another 3 to 4 kilograms. 

Since my body has already adjusted to my current lifestyle, food intake and weight, will it take me another long year to lose a mere 4 kilograms?

Why is it so hard?

pearlie