Guilt in a dream usually points to something unresolved -- a wrongdoing, real or perceived, that your conscience hasn't let you set down yet. Confessing in the dream can reflect a wish to finally address it directly, while being unable to explain yourself often names how stuck the self-blame still feels.
Mars conflicts with those who are ruled by Venus, and Venus conflicts with those ruled by Mars. - Picatrix (Andalusia, ~1000.AD)