Why is this the answer?

The answer is pride because this clever riddle uses the word "swallow" in two very different and smart ways to describe a feeling everyone has. Pride is the feeling of being happy with yourself and what you have done. For example, you might feel a rush of pride after you finally learn to ride your bicycle or when you get a gold star on a tough test. Let us look at the first part of the riddle: "What can be swallowed." This part is talking about when you feel a little too proud, and you need to "swallow your pride." This is a special phrase we use when someone has to admit they made a mistake, even if it is hard to do. For instance, maybe you told your friends you were the fastest runner, but then you lose the race. It takes a big person to "swallow your pride," admit someone else was faster, and congratulate them. You are choosing to be humble and honest instead of letting the feeling of being upset control you. Now for the second, trickier part: "But can also swallow you?" When a feeling "swallows you," it means that feeling has grown so big it takes over your good sense. If you let your pride get too large, it stops being a happy feeling and starts making you act unkindly. You might stop listening to your teacher, ignore helpful advice from your parents, or think you are better than your friends. When that happens, your pride has "swallowed you up." It blocks you from learning new things and making good decisions, which can cause problems for you. The riddle is trying to teach us that pride is great in small amounts, but too much can be dangerous. It is a puzzle about balancing a happy feeling with a humble heart.