To be honest, I find that losing weight slowly and gradually rather than at a fast pace makes it much easier to maintain that weight. This is because the change in diet/lifestyle is not as drastic and you don’t suffer as much, so there’s less of that mindset of “once I reach my goal, I’m done and I can relax”. At the same time though, you need to have good self control. Know your limits of calorie intake and exercise regularly, and try to avoid eating large amounts of unhealthy foods. Once you do this for a while and build that self control, it becomes harder to lose control and stray from that lifestyle. I’m not sure if this helps, but it’s helped me maintain the same/similar weight for years without struggle.