A man’s heart disconnects from God when he commits a sin leading to the relapse of the heart. His heart will be attracted to the falsehood and will lose all of its good characteristics.
Abu Abdullah (as) says:” My father used to say: nothing is worse to the heart than a sin. When a heart is drowned in committing sins, it will end up controlled by sins until it is attracted to falsehood”. 
Abu Abdullah AlSadek (as) says:” If a man commits a sin, a black spot is present in his heart. If he repents, the black sport will be erased. Otherwise, if he commits more sins, the black spot will control his heart and he won’t ever achieve success”. 
A Man loses the Sweetness of Remembering God by Committing Sins:
Faithful hearts feel the sweetness of remembering God, a sweetness that no sweetness is above it. But when the heart is relapsed, he will not ever feel this sweetness the same as when a patient stops feeling the taste of delicious food when his health is relapsed. This doesn’t happen because food loses its taste, but because the patient loses his appetite. Hearts are the same, if they relapse they will lose the sweetness of remembering God and never be attracted to it.
It was mentioned in the hadith:”God has revealed to David: among 70 internal punishments, I will deprive he who doesn’t obey my provisions from the sweetness of my remembrance”. 
A man came to Al Imam Ali (as) and said:” O, the Commander of the Faithful, I am deprived from praying the night prayer (Salat Al Layl) so Al Imam Ali (as) answered him:” Your sins have chained you”. 
Al Imam Al Sadek (as):” A man who commits a sin will be deprived from Salat Al Layl; a bad behavior is faster in sticking in a man than a knife pierced in a flesh”. 
Sins that Block Du’a (supplication):
Having a disconnected heart from God is among the direct impacts of commiting sins so the heart will no more interact with God.
Supplication is among what a man ascends to God almighty, that’s why we say: supplication is the ascending Quran which a servant ascends to God after receiving the descending Quran. Therefore, if a man is disconnected from the ascending Quran (supplication) he will surely be disconnected from the descending Quran so God blocks his Al Du’a and his needs will not be fulfilled. Even if he was needy oneday and supplicated for God, The almighty will block his Du’a and won’t answer his needs.
Imam Ali (as) says:” A sin blocks fulfilling supplication”.
A man asked Al Imam Ali (as) about God’s almighty saying ” Call on me, I will answer your prayer”: Why aren’t our needs answered despite our supplication? So he (as) says: which supplication will God answer after you close all His doors and way? Repair yourselves and your deeds, purify them from inside, enjoin good, and forbidden evils so that God will fulfill your supplication”. 
Al Imam Ali Bin Al Hussein Zain Al Abidin (as): “A Sin that blocks answering of supplications and prevents the heart from the truth is the disobedience of parents.”
In another hadith:” Sins that block Al Du’a are: evil intention, self godlessness, double-dealing, uncertainty of God’s answer, postponing the obligatory prayers after their time, not being connected to God almighty by kindness and charity and saying bad words”. 
Abu Jaafar Al Baker (as) says:” A servant asks his God for a need, so God decides to fulfill it for him soon. If the servant commits a sin, God almighty says to the angel: do not fulfill his need, and deprive him from it because he stimulates my anger and deprivation". 
Supplication of Ahl Al Bayt (pbuh), His Eminence Al Sheikh Mohammad Mahdi Al Asfi- freely
 Bihar Al Anwar part 73, page 412
 Bihar Al Anwar part 73, page 327
 Dar Al Salam for Al Sheikh Al Noury 200: 3
 Ilal Al Sharai (Reasons of Laws) 51: 2
 Osoul Al Kafi 2: 272
 Bihar Al Anwar 93: page 376
 Meaning of News (Ma’ani Al Akhbar) 270
 Meaning of News (Ma’ani Al Akhbar) 271
 Osoul Al Kafi 3: 373