Been there done that...now I'm fat

Hey there I am a 23 year old male until recently I worked at McDonald's, from 16 years old till 22, I am currently overweight on my bmi, during a two month period I was on a extremely strict diet of oats, chicken rice, chicken veg plenty of water, for a solid two months that's all I ate and drank and lost 2 stone in two months, however it felt really easy like I could do it whenever I wanted so I didn't take it seriously, now I'm abit older I am finding it difficult to stick to a diet plan so strict, I guess it's a mental mind game!