My third baby is almost 18 months old and has already started having tantrums. I remember this time with my older two. They literally go from being a sweet cuddly baby to throwing fits over night and you try to figure out what went wrong, but here is the truth: it is developmental. All kids go through it and it is part of how they learn. They are not good at controlling their emotions at this age and throwing fits is part of how they communicate to you. The good news is that you are not alone, and there are a few things you can do to help avoid tantrums and diffuse them in the moment.