Power of Prayer?:

Not sure how prayer works. Can we (or the saints) actually convince God to change things? I am convinced of the power of prayer after seeing its positive effects when my father needed them, yet not sure how it works. Do we need to pray for our own self-journey or does God actually change his mind about how things work. Not sure if prayer is that important. I understand that communicating with God keeps the relationship strong, yet the one-sidedness feels very empty.