Should we pray for things we want or just have faith that HaShem is already hearing us and will fulfill our needs without even praying but just believing?
Hashem knows our needs better than we do, and our prayer is not to inform Him as to what our needs are. In fact, it is only because of his divine decree that we are in this situation in the first place. So why do we have to pray? The reason is because Hashem specifically wants us specifically to pray for our needs, and He set the world up in a way that we have to pray to Him in order to get our needs. When we pray, and vocally acknowledge our need, and ask Him to help us, we come to the realization that He is the one giving to us, and we will then feel humbled before Him. Secondly when we ask for our needs, and then receive them, we will be thankful, and express that thanks to Him. This is similar to a father, whose son went off to school, and he never calls home. The father feels that it is important for his son to keep up a connection to the family. What does he do? He doesn’t send him money, until he calls, and then when he calls, he’ll send him money for a few weeks. This way he’ll call again. If he would just send him money for the whole year, he might not hear from him again until next year, and they will grow apart.
This is why Hashem specifically wants us to pray everyday, in order that we keep up our connection with Him, which is ultimately to our benefit.
Rashi’s commentary to Genesis 2-5, Tractate Yuma 76a.