There is courage in walking a path when you know others have walked it before you. Krishna tells Arjuna: knowing this truth, even ancient seekers who longed for liberation performed their duties. You should do the same, following the way they followed long ago.
This is not an abstract instruction. It is the reassurance of an elder saying: your great-grandparents tilled this very soil and the harvest came. Trust the method. Walk the path. The tradition is proven, and you are not alone in it.