I think part of the reason, is that there’s a mental battle about whether something is exactly a sin etc. For eg. we all know that ‘anger’ or malice is a sin, however there is also something such as ‘righteous anger’, and then there is the sin of gluttony where we eat too much - but how often do we eat too much? eg. at weddings, social gatherings, christmas, etc. We always eat too much in western societies. We are all glutons at times. I guess we / I rationalise that ‘another piece of cake isn’t so bad’.
another example; some would say that you have to fast for 1 hour before communion, but if you didn’t, do you really think that’s a sin… The battle is between what we / I know about what the church teaches, and what we think in our heads. Personally I believe the church is right, however I don’t always understand it. There’s the disconnect between believing the church and our own understanding. And then of course there’s the ever present views of the world which often bellow much louder than the voice of the church. the world will say ’ have a glass of wine to get rid of that anger’. The psychologist will say ‘take a pill or blame your parents re. your present behaviour’
Of course there is a disconnect between our belief in God and our understanding of God. We believe that our body is the temple of the Holy Spirit and so is that of other people; but how do we begin to understand such a thing? Its like how one of the prophets in the old testament thought that God wanted him to kill his son as a sacrifice; today we would say - of course God doesn’t want that, and its against the 10 commandments - but this prophet actually thought God wanted him to kill his son as a show of his love for God. That clearly was not right.
And the biggest battle of all - how to get a priest/spiritual director? they’re so busy, hard to find, and only human anyway - which in my experience has been the great excuse for many things.
And how best to spend your time? praying? working hard at your job / housework? or working out how not to repeat your favourite sins?

