Ultimately, failure in prayer involves failure to measure according to truth. We fail to see what prayer really is, the requirements to be met, and the steps to be taken. This happens when we measure according to our own understanding instead of asking God to show us the truth of these things.
There is a name for measuring according to our own understanding: pride. Our understanding of pride is measuring oneself more highly than one should: i.e. more highly than one really is in truth. It is close to what pride really is, but inaccurate and incomplete enough to hinder our prayers.
If a person measures according to their own understanding instead of asking God to show them the truth, they are measuring themselves more highly than they should. They are measuring themselves as capable of perceiving the truth without God’s help. The truth is we are not.
We are blinded by pride. If we see, but are unable to perceive what we see according to truth we are effectively blind: measure blind. We fail to see what prayer is, the forces of prayer that produce results (love, faith, patience, humility, etc.), and the forces that hinder prayer (sin, fear, doubt, pride, etc.).
Pride is particularly dangerous as it works to blind a person to itself. It is very difficult for a person who measures according to their own understanding to see that they are operating in pride: measuring according to their own understanding. It is a truth we need God to show us.
What does the scripture say about pride?
Only by pride comes contention: but with the well advised is wisdom. (Proverbs 13:10)
Does the measure of what pride is fit what the scripture says. Contention only comes by pride. Contention is disagreement about what is true. It is disagreement about what was, what is, what will be, what should be, what is possible, what the value of a thing is, etc.. If two or more people seek and receive the truth of these things from God they share the same perception of the truth. There is no basis for contention.
When pride comes, then comes shame: but with the lowly is wisdom. (Proverbs 11:2)
He that answers a matter before he hears it, it is folly and shame to him. (Proverbs 18:13)
Shame comes after pride. Shame comes to a person who answers a matter before they hear what God says is true.
Pride goes before destruction, (Proverbs 16:18)
Trust in the Lord with all your heart; and lean not to your own understanding. In all your ways submit to him, and he will direct your paths. Be not wise in your own eyes: fear the Lord and depart from evil. (Proverbs 3:5-7)
We depart from evil, from the path of of destruction, when we seek God to show us what is true - what our next step should be.
What does the scripture say about pride and prayer?
God resists the proud, but gives grace to the humble. (James 4:6)
Whatsoever we ask, we receive of him, because we keep his commandments and do those things that are pleasing in his sight. (1 John 3:22)
Pride, measuring according to our own understanding, is not pleasing to God. It causes us to fail to meet one of the requirements for successful prayer. In fact, it put us in a position where God resists us. On the other hand, God gives to those who seek him for truth.
Is Jesus Lord of how we measure truth, or are we self-willed? We are either submitted to Jesus in how we measure truth, do his works, and receive his provision; or we are submitted to Satan, do his works, and receive of his wages.