Because it is sinful it does not satisfy and it becomes a habitual force in one's life. At morning light they practice it, because it is in the power of their hand. If marriage and its intimate relationship reflects Christ and His Bride, then we can know for sure that masturbation does not belong in a Christian life. In the same manner we have to consider each other in marriage. Christians have to discipline themselves and if you are not disciplining yourself you will feel guilty.
Guilt feelings are the results of sin.
I am glad that you're reading this writing. Hopefully your conscience is bothering you, so you will desire to change. Sin separates us from God, and so does the lust of the flesh. Committed sin and addiction to lust cannot always be blamed on satan. Neither can sexual fantasizing.