As I've already shared...
Prayer only fails when a person is lacking in faith and NOT praying GOD's WORD, to back up what their praying and believing HIM for. But, you MUST come through JESUS to get to GOD, my HEAVENLY FATHER (John 14:6 KJV). In other words, whoever comes to GOD, in prayer, must believe that HE is GOD and a REWARDER of them that DILIGENTLY SEEK HIM (Hebrews 11:6 KJV)! So, you're right prayer does fail all the time for those who are not praying according to GOD's HOLY WORD, the BIBLE because HE said in HIS WORD that HIS WORD shall not return to HIM void. This means that if you're believing and praying to GOD to heal someone from cancer or any sickness, disease, illness, etc. YOU MUST PRAY HIS WORD BACK TO HIM!
For example, let me teach you how to pray GOD's WORD back to HIM to get your prayers answered: " Dear HEAVENLY FATHER, YOU said in YOUR WORD that "by HIS (JESUS) stripes we were healed" (Isaiah 53:5 KJV). Therefore, I decree and receive that by JESUS' stripes I am already healed from the satan' evil spirits of any and every terminal illness, sickness, and disease and curse them at the root and seeds of them in my mind, my heart, my body, my soul, and my spirit and send them back to the devil-satan and all his followers NOW in JESUS NAME!!! And, I decree that NO weapon formed against me shall NOT prosper against me" (Isaiah 54:17 KJV) because FATHER GOD, YOUR WORD from Psalms 91 is manifested in every area and aspect of my life including my mind, my heart, my body, my soul, and my spirit NOW and FOREVER in JESUS NAME!!! Amen!!!
So, in order to get your prayers answered by the ONLY TRUE AND LIVING GOD, you MUST take HIM at HIS WORD because IT will NEVER return to HIM void (or unanswered) (Isaiah 55:11 KJV). GOD always answers according to your faith in HIS WORD (Matthew 9:29 KJV). In JESUS NAME, GOD Bless...
Lastly...So, now do you understand what praying is all about?
6 Be careful for nothing; but in every thing BY PRAYER and supplication with thanksgiving let your requests be made known unto GOD.
7 And the peace of GOD, which passeth all understanding, shall keep your hearts and minds through CHRIST JESUS.
Again, In JESUS NAME, GOD BLESS!!!