Hitherto have ye asked nothing in my name: ask, and ye shall receive, that your joy may be full.
Note 88 at Joh 16:24: The proper way to pray is to the Father in the name of Jesus. While Jesus was on the earth, the disciples asked Him for whatever they needed, and Jesus would ask the Father and get it for them. Here He was saying that they should not ask Him anymore, but they should take their requests directly to the Father.
Note 89 at Joh 16:24: Asking in the name of Jesus means that God treats our requests the same as He would if Jesus was personally making the petition. Therefore, we can expect the same treatment from God as Jesus would get. In the business world, that is called the power of attorney.
Those who pray in the name of Jesus but then doubt that God would answer their prayers because they aren't holy enough are taking the name of Jesus in vain. If people pray in Jesus' name, then it is His holiness that God looks at and not theirs.