A square block won't fit in a round hole. Shoes feel funny, and socks don't seem to come off right. And to make matters worse, you won't let them climb on top of the kitchen table.
Toddlers have tantrums because they get frustrated very easily.
Most toddlers still do not talk much. They have trouble asking for things and expressing their feelings. Toddlers also have very few problem-solving skills. Tantrums are most likely to happen when toddlers are hungry, exhausted, or over-excited. Preschoolers are less likely to throw tantrums.