Come to think of it, if there is ancestral curses, what of ancestral blessing. Over emphasis on one side of truth will lead one into error. The ten spies over emphasis the existence of the giant (Obstacle) in the land of Canaan at the expenses of the blessing (milk and honey). They were disqualified by God (Num. 14). The truth is, if what my ancestors have done negatively affect me, then what they enjoy must not elude me. Therefore if you find any curses in your ancestral line, deal with it, but don't fail to posses the blessing.