This is a great question. You need a good mix of wet and dry ingredients, and nothing cut too chunky. If it is too wet, it will just spread out and turn mushy on baking, if it's too dry, it will just crumble. However, you can be fairly sure if you follow my recipe above that your meatloaf will stay whole! If you are a little unsure, I find it works really well to pack the meatloaf into a loaf tin and refrigerate for several hours too.