There are a few things you can do to prevent your sushi from falling apart: * Cook the rice properly. Be sure to rinse excess starch, use the right rice-to-water ratio, and season hot rice before assembling rolls. * Don't overfill. When you're spreading your rice, you want to make sure to leave a space at the top of the nori sheet without rice. * Gently squeeze the roll. As you roll your sushi, you want to gently squeeze the roll to tighten it and compress the rice, which will help your sushi roll hold together.