A very common motivation to employ projections is harvested from justifications of our resentments and despairs, angers and fears, etc. Resentments are described as re-feelings of bad experiences -- such as when your father cheated on your mother.
These resentments can feel even stronger then the original offense when we expand on them to the point of projections -- meaning things become even worse as we re-live those re-feelings again and again.
Thanks Robby..... I needed to hear that again.