How do i retain my current body size and lead a healthy lifestyle since i just finished dieting and have reached my ideal body?

Diet and exercise: It's often said "diets don't work" because when people go back to eating like before dieting they tend to regain the weight they lost. It's necessary to maintain a healthy diet at all times. See http://authoritynutrition.com/weight-loss/ for general guidelines on maintaining a healthy weight. Exercise helps too. It may be highly beneficial to join Weight Watchers or a similar group for support.

Dieting.: basically, if you had to diet, your regulatory controls of what to eat are broken and never coming back. You can only decide if you are gaining or losing weight that day. Typically people gain 2 pounds, go back to dieting to lose it, gain/lose/etc. BUT at ideal weight, this is ok. Exercise is probalby MORE important for weight control.