The Japanese are picky eaters. They eat strange and exotic foods such as raw fish, with unheard of methods of cutlery utilization. They are also the source of four months of research into how to eat the ultimate American food: The Hamburger, without resorting to American television's table manners.
Firstly take a look at your burger. What I usually do prior cutting it with knife and fork is push down on the bun to make it more like a sandwich. The Japanese say nothing of it, but I do think it will help stabilise the meal a bit. I pushed down on my burger as always, but instead of cutting it and eating via cutlery, I attempted to follow the method that follows. I am pleased to say my attempt was met only with success.
Onto the Japanese recipe:
Put your pinkie and thumb of each hand, on both sides below the meat sandwich / meat in a bun. You will note that in doing so you have created a stable platform for the foodstuff to rest upon. To prevent an avalanche on the top part of the meal, place all three remaining fingers of each hand like a bear trap over the top of the burger. All sides have adequate pressure, and now you are good for the eating. Place the food in your mouth while maintaining your human bear trap. Bite down and continue to eat. You will be amazed to have not spilt at all (one hopes).
I attempted this great method today, and I am glad to state that not a drop of sauce left the burger once I had it in this clasp. A horrible meal to eat, harking back to the days when mankind ate raw meat, has thus been converted into a civilised meal... thanks to research by people who eat raw meat.
You might thank me later. Try this method. It really does create great joy.