The 4 ways the Propagation Of Sin is spread into the world is by...
1 ~ the bad things we think of
2 ~ the bad things we say
3 ~ the bad things we do
4 ~ & the GOOD things we FAIL to do
Of all these, number '4' is neglected the most, 'the GOOD things we FAIL to do' which is the 'Sin Of Omission'
The above is derived from a portion of the common Catholic Prayer, the 'I Confess' which reads "and in what I have failed to do".