Subsequent fasts are easier because you have less toxins.
When you eat, say, hydrogenated trans fats, which are fats in modified form, they are stored directly in your cell membranes without any molecular change, at only 3% calorie cost from your lips to your hips. These fats stay there, until they are metabolised, which for many of us is never. Their unusual molecular structure were not designed for your bodies systems, thus you get more prone to cancer, because they leave gaps in your cell membranes which were not meant to be there, thus allowing carcinogens to be introduced. They also raise cholesterol and tri-glycerides which cause artery damage.
When you fast or lose weight by eating properly, you metabolise these modified fats and other toxins, and this is why you had your bad experiences on your earlier fasts. Now you are eating more carefully, you don't get the detox so much.