@Nared That's what keeps happening to me. I think I should've saved the snowman pieces because they restore nearly all of your HP (assuming you're at LV 10). That would make it a lot easier. That being said, if you ever attempt the genocide route again, GET THE SNOWMAN PIECES! With the remaining space in your inventory, the best healers would probably be the pie you get from Toriel, which I believe is gurenteed to restore all of your HP, and the cinnamon buns which you can steal from the shop in Snowdin.