it happens for one main reason- the boot doesn't fit. remember boots should always be snug but not painful tight, especially when new. even for riding park or strictly jibbing, they still need to be locked down on your feet. skateboarding, inline, wakeboarding, etc teach us that loose and comfy is better since range of foot motion key for those sports. in skiing, however, all your weight and energy needs to be transferred to the flex of the boot. if the boot feels way too small, take it to a real bootfitter (not dick's or sports authority) and they can usually grind or stretch the boot to squeeze out some extra room, but if the boots are too big, get new ones. doubling up on socks or jamming paper towels in the toe box wont help anything. your leg moves in the cuff, which slams your toe into the end when skiing. if the boots fit, feel snug, and it's still happening, make sure you buckle them in the correct order. your feet may just be buckled too far forward in the boot. do the top 2 buckles and strap first and make sure they are tight before moving on to the lower 2.