Do I have to diet for the rest of my life?

I'm thinking of starting a diet these days, and a question suddenly popped into my head.

I am wondering if I only need to work hard during the weight loss period, or if I will have to manage my diet and exercise for the rest of my life.

I've noticed that there are many people around who continue to manage their weight even after successfully losing it.

I am wondering if it is possible to maintain my weight even if I eat as I used to once I reach my target weight.

I would appreciate advice from those with experience on whether I need to manage it like a lifelong diet to maintain it without the yo-yo effect.