Why can't I lose weight?

Six years ago I lost two and a half stone in six months and dropped from a size 18 to a size 12. I've kept the weight off since, which is a good achievement I'm proud of. But I'm still at the top end of what would be a healthy weight for me. A few pounds over and, strictly speaking, I'm overweight (according to standard health guidelines). I'd like to look slimmer anyway. Size 10 would be ideal.

So why can I not lose one more stone? I've been trying for two years now and I just stick at the same weight. Despite still following Slimming World. Why the plateau? I just don't know exactly. I've lost some kind of slimming mojo and generally spoil my efforts by eating just that little bit too much of what's fattening. How to get the willpower back?

Sue x