To avoid a sense of loss of sin that is prevalent in our culture, we need to remember that the root of sin lies within us. That root goes back to the sin of Adam and Eve and we name it concupiscence. 

Jesus speaks of the various concupiscence within us in the Gospel. For many of his day, it was thought that a person became ritually defiled by contact with something that was considered unclean, such as eating unclean animals or touching a leper or a corpse. Jesus rejected this. Instead, he said what makes a person unclean is acting on that which leads us to sin from within, such as lying, stealing, murder, etc. These areas of sin are within each of us. The Evil One tempts us to act out in these areas and thus we sin. 

The adage "the Devil made me do it" is not true. the Devil tempts us, but we made a conscious choice to act out.  As St. Paul said: I do the things I don't want to do; and do not do the things I should do. Why? There is a law of sin within me. 

Am I hopeless? No! For the grace of God through Jesus' death and resurrection is given to me to turn away from the temptation and to choose to do what is the will of God, what is good, pleasing and perfect. It is my choice to sin or not to sin.