I've been overweight for as long as I can remember, with various short-term attempts of losing weight. I went to 150kg (24st) over the course of 15 years, which never made me realise how bad it actually was.
After losing 26kg (4st) during my time at university and putting it back on in the two years that followed, my final wakeup call was a colleague's wedding. I needed a suit, I could chose from two in the entire store that would fit. Traveling to the wedding and barely being able to fit into the plane seat was even worse. The biggest moment though was the public embarrassment of not being able to fit into a seat outside a café - it wasn't that I got stuck in the chair or something that you are usually worried about when you're overweight and very conscious of it, no, I couldn't fit in in the first place and it wasn't even close!
That all brought the little things to my attention that I had discarded all too easily in the past. Occasional pain/numbness in the knees, having trouble tying shoe laces, feeling like all eyes are on you at all times because you're the tallest and biggest person in the room.
That was almost four years ago, and I'm happy to say that while I'm still not done, I've managed to lose a fair bit of weight and to keep it off. There have been setbacks, there has been the occasional stone that I ate back on, but overall I'm going in the right direction, and this time I'm not going to give up.