Arjuna's defeat by the Abhiras

 After the yadavas in dwaraka killed themselves in fighting among themselves and krishna's death,Arjuna was taking the wives of the yadavas to hastinpaura.While he was on his way,he was attacked by the Abhiras,a tribe opposed to the yadavas.They knew the yadavs had died,and they attacked the women who had precious belongings as well.But Arjuna coudnt so anything.With difficulty he lifted the gandiva,and shot arrows,but they fell short of them.He coukdnt invoke celestial weapons.He then fought them with hand to hand,but he could save krishna's eight wives,and some important yadava women.But The Abhiras,peasants who attacked took away some woman,and their belongings.This shows that Arjuna is not a great a warrior as he is projected to be.At that age,he could be in his seventies.He is not older than Bhishma  or Drona at the time of Mahabharata war.They have fought in the war well.But Arjuna's defeat by the Abhiras,peasants also show another thing about Arjuna's valour.He is not good in hand to hand combat.He is good when he has his gandiva.He basically learnt  dhanurvidya.And he didnt have to fight other weapons like mace,sword with others.Without the bow,even nakula,sahadeva are better warriors than him,But in this situation,hand to hand combat is needed.And at this age,he couldnt fight the thieves.
In the mahabharata war,he fought with those who were following rules of war.Like Karna,Bhishma.And he could kill them when chariot wheel is sunk in earth,or using shikhandi as a shield.But the Abhiras,peasants didnt follow any rules of war.So Arjuna got defeated by them.He was punished for killing karna unrighteously.And krishna who asked karna to be killed when his chariot is stuck,he also got killed like a  hunted animal.This is the result of his advice of Adharma yuddha and making pandavas kill their enemies,by unrighteous means.So he was punihsed for his karma.
So one shouldnt do Adharma,otherwise one will be punihsed for these things.