Praise is a word that is often partnered with worship, and it is sometimes understood to be essential to worship. There's nothing difficult in understanding the intent of praise - it is to demonstrate approval for what one is doing or has done. It is to acknowledge that they are the one who is to be recognized. Praise is both relational and social at the same time. Praise is given to advertise that something is of value and should be exalted.
But, why might it be essential to worship? In worship, we are communing with God to change and become more holy - this change often means hard roads we need to follow, and obviously we don't easily "approve" of a direction that is hard, particularly when we are in the midst of hardship. When we don't approve of the directions of God, we are in not praising Him for his wisdom, and we don't acknowledge Him as sovereign.
Yet, we still need to praise God in times of struggle ... this is the sacrifice of praise that scripture describes.