Hare Krishna Gauranga Prabhu, Sorry i did not put my words in details. I am referring to poorva punyas or punyas of previous incarnation. Rahu , when it is good it just gives you the results of those poorva punyas in a fast forward kind of thing. Ketu is mokshakarka. For moksha it should remove all your karmas and effects. So it will give results of previous bad deeds and will remove them one by one. It works in a magical way and leads you to liberation.
Guru dasha is good in context to rahu dasha. Eating mear etc does not make a person bad. It depends on position of planet to futher understand it.
Alok Jagawat