Calvinists: Why did Jesus teach us to pray God's will to be done? Isn't He capable of doing it without us?

It reminds us each time we pray that we depend on Him for everything. Having all knowledge and all power in no way is a reason why we shouldn't ask Him for things. We don't know the answer, even though He does. It's the same reason why we share the Gospel with everyone, yes, even as "Calvinists, or reformed" because He tells us to. It's not up to us to know if that person will accept or deny Christ...we are to be obedient regardless. It's the quickest way to learn humility, ask the unseen God for what you need to live.