Go ahead and pray!

As any earthly father has the authority and right to change his mind in regards to the family's business so does God our Heavenly Father. Should we limit God and His authority in this respect? Scriptures states clearly that He changed His mind on more than one occasion. Should we argue with God's Word in this matter and just work around it? If the fervent prayers are supposed to avail much but then one believes that God will not budge on future outcomes then what is truly being availed in prayer? Scriptures state that prayer can and doe affect future situations so by all means go ahead and pray without ceasing because so much truly can be availed...