The repeated emphasis on that instruction is asking in Jesus’ name. Since Jesus Christ is the Mediator between God and men, to ask in Jesus name is to ask with the knowledge that what you are asking for is consistent with God’s will, and so you can append the name of Jesus to your prayer with confidence.
1 John 5:14 says, “And this is the confidence that we have in him, that, if we ask any thing according to his will, he heareth us.” So the most important issue is praying in accordance to God’s will, and you do that by knowing the Bible. It is aligning your will along with His will, and desiring what Christ desires for Himself, which allows you to pray in Jesus name with confidence that His redemptive work has purchased the answer for which you seek.
Ask yourself, are your prayers focussed upon requesting what you know is the will of God? They ought to be.