If you are a believer in Christ and you are not filled with love, joy, peace, forbearance, kindness, goodness, faithfulness (the fruit of the Holy Spirit) there is a reason.
You have been going to church, reading your bible and praying, but you are not much different than before you gave your life to Christ
The reason can be that you have a stronghold in your life, an area in which the enemy of God has a foothold. You may have been a christian for many years, but there is an area that is controlled by the enemy. this will keep you from changing.