Repeated sins with out seeking forgiveness cause seal on the heart. Every sinful act causes a blot on the heart which can be removed by sincerely seeking forgiveness. When the sinful deeds are repeated, the black blots cover the heart and seal it. The person with sealed heart does not feel the taste of Prayers or Du'a or Quran etc. Sealed heart is like a dead heart.
Removing the seal from the heart is always possible if the person is really willing and ready to act to remove the seal. It starts with sincere repentance and seeking forgiveness and establishing a firm decision not to commit the sins again.
Repeating Estighfaar, with deep feeling of sorrow for committing the sinful acts, is very important in this regard.
Returning back the rights to the victims is also very important.
Performing all Prayers on time as well as reciting Quran, Du'a, Ziyarat Ashura, Night Prayer is very helpful.