Why should we pray for our ancestors during shradh?
Psychologically and scientifically, shradh is a form of attachment or guilt within us that restricts us to lead a normal day to day life. It disturbs and haunts us day and night in our thoughts as we have a feeling of regret within us for the dead person. Thus shradh ceremony or any such offerings are the ways to fulfill the unfulfilled desires of our ancestors. It is an act to remind us about the execution of their pending jobs. By remembering our forefathers and seeking their blessings at the beginning of any auspicious work helps us to relieve ourselves from self-confessions.
Seek prayers and blessings from your ancestors: http://shubhpuja.com/pitrasantushti-id-736174.html