Having a healthy kind of pride is good! However, pride can also mean conceit, arrogance, or superiority. This kind of pride is based on self-centeredness, and it is pernicious. For example, when pride overcomes ones judgment, it makes them believe that they never do anything wrong. Having too much pride can ruin your life, it can hurt relationships and it can even make you lose your job. When one gets to the point where they believe that they are practically perfect, that is when pride can be hurtful. Pride can also be harmful when one puts too much pride in something. For instance, say someone put all their pride in their job, they made is so their job basically defines them. Now say that person loses their job, they'll feel like they lost everything simply because they let their job define them. In a situation like this where someone puts all their pride in something, pride is very hurtful because it is not guaranteed that you will have said thing they put all their pride into, so what will happen if they lose it?
Hope this helps! :)