Absolute Faith In God Is Difficult

And without faith it is impossible to please him, for whoever would draw near to God must believe that he exists and that he rewards those who seek him. (Hebrews 11:6 ESV)

God is absolute and He demands absolute faith in Him. Herein lies our difficulty. We find it impossible to have absolute faith in anything. I can think of there are three possible reasons for this:

Our Daily Experience
Thus saith the LORD; Cursed be the man that trusteth in man, and maketh flesh his arm, and whose heart departeth from the LORD. (Jeremiah 17:5 KJV)
Love never ends. But as for prophecies, they will come to an end; as for languages, they will cease; as for knowledge, it will come to an end. (1 Corinthians 13:8 HCSB)

We never have absolute faith in anything because all things around us are imperfect. They will fail. My car has a GPS, which will give me information one step at a time. I find this very frustrating, because I would like to know in advance the route it is going to take and decide if it is the best route. This GPS usually gives the shortest route. Sometimes, the shortest route goes through the city and because of jam and traffic lights, it is better to go by the expressway. So I cannot place all my faith in the GPS. This is just one of the many examples why we never have absolute faith in anything.

Our Flesh, The Old Man
So I find this law at work: When I want to do good, evil is right there with me. For in my inner being I delight in God’s law; but I see another law at work in the members of my body, waging war against the law of my mind and making me a prisoner of the law of sin at work within my members. (Romans 7:21-23 NIV)

We have differently fleshly desires from the spiritual God. Our body has its own desire which it expect us to fulfil. We also have different goals and ambitions from God. This put us into conflict with God's will and if our desire is strong, we cannot discern God's will.

Satan
Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour: (1 Peter 5:8 KJV)
Above all, taking the shield of faith, wherewith ye shall be able to quench all the fiery darts of the wicked. (Ephesians 6:16 KJV)

Satan is ever present, putting temptations and evil thoughts into our mind. Satan will always help our flesh to gain its way.

Be perfect, therefore, as your heavenly Father is perfect. (Matthew 5:48 NIV, HCSB)