When you pray, do not keep on babbling like the pagans, for they think they will be heard because of their many words. (Matt 6:7)
There are few more irritating things to a parent than the constant nagging of a child, especially when what they have asked for has been promised them and all they have to do is wait.
Sacrifices and Offerings
In Leviticus clear laws are laid down about the worship in the Tabernacle. Sacrifices were to be made for various reasons - as thanksgiving to God or for forgiveness of sin, for example. For each of these sacrifices the particular animals or birds required are specified. Sometimes the size of the sacrifice was according to the means of the worshiper, as in the sin offering. On other occasions the sacrifice made was to be the same for everyone, as in the guilt offering. But God never said that a greater offering would bring a greater blessing.
So it is with our prayers. If we keep babbling on as the pagans do, reciting endless words, it does not improve our chances of receiving an answer. God would just as soon hear a simple, "please will you help me," than a lengthy list of all the reasons why He should help.
There are times when intercession for something involves lengthy times of prayer and persistence, occasions when our wrestling in prayer is really about us finding the faith or the strength to accept God's will (the prime example being Jesus in Gethsemane). But with our simple daily needs, He already knows (Matt 6:8) and vain repetition is pointless.
Sin and Confession
Perhaps the times we are most tempted to go beyond what is necessary is when we have sinned and feel we have let the Lord down. He has made a simple provision for us - if we confess our sin He is faithful and just to forgive us our sin and cleanse us from all unrighteousness (1 Jn 1:9). But how often do we find ourselves returning to God time after time because we still feel guilty, we still want to make restitution. We can be down on ourselves for hours, days or even weeks if we've failed particularly spectacularly.
But God only requires us to confess and repent once. He forgives us and He expects us to take hold of that forgiveness and move on. The devil wants to keep us bowed down by our sin and feeling guilty for as long as possible because he knows we're no use to God in that state.
Prayer College Assignment
Don't compound your sins by continually dwelling on them. Confess, repent, accept the forgiveness Jesus died to purchase for you. Then move on.