Forever to lose, RAPID regain.

I spent lots of time & effort trying to lose 6 pounds. It's about 10-12 I want to lose all together.

I felt great, had lost that weight with counting, and then as soon as I began to stop obsessively counting calories, it all came back VERY FAST. WHY??? it's not like I pig out, just ate more normally.

How to avoid the regain & maintain the weight loss for long term?

I am 5'9, and now I weigh 155. Ick. I am age 38. Goal is at least to 145. Have not weight that in years, so maybe body just wants to rebel against it.